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 $177.60   9.684%   $194.7988   $194.80   $194.80   $194.80  
  Purchase #2 $146.74   3.745%   $152.2354   $152.24   $152.25   $152.20  
  Purchase #3 $89.34   5.253%   $94.033   $94.03   $94.05   $94.00  
  Purchase #4 $143.69   4.332%   $149.9147   $149.91   $149.90   $149.90  
  Purchase #5 $234.67   5.111%   $246.664   $246.66   $246.65   $246.70  
  Purchase #6 $146.30   12.474%   $164.5495   $164.55   $164.55   $164.50  
  Purchase #7 $209.52   11.243%   $233.0763   $233.08   $233.10   $233.10  
  7 purchase totals = $1,147.86       $1,235.2717   $1,235.27   $1,235.30   $1,235.20