Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $195.56   3.403%   $202.2149   $202.21   $202.20   $202.20  
  Purchase #2 $215.59   9.316%   $235.6744   $235.67   $235.65   $235.70  
  Purchase #3 $160.31   10.842%   $177.6908   $177.69   $177.70   $177.70  
  Purchase #4 $214.27   11.605%   $239.136   $239.14   $239.15   $239.10  
  Purchase #5 $237.32   11.829%   $265.3926   $265.39   $265.40   $265.40  
  Purchase #6 $182.52   3.750%   $189.3645   $189.36   $189.35   $189.40  
  Purchase #7 $120.90   9.314%   $132.1606   $132.16   $132.15   $132.20  
  7 purchase totals = $1,326.47       $1,441.6338   $1,441.62   $1,441.60   $1,441.70