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 $117.62   7.178%   $126.0628   $126.06   $126.05   $126.10  
  Purchase #2 $97.41   5.266%   $102.5396   $102.54   $102.55   $102.50  
  Purchase #3 $180.51   7.244%   $193.5861   $193.59   $193.60   $193.60  
  Purchase #4 $121.52   7.205%   $130.2755   $130.28   $130.30   $130.30  
  Purchase #5 $182.29   10.817%   $202.0083   $202.01   $202.00   $202.00  
  Purchase #6 $146.93   5.272%   $154.6761   $154.68   $154.70   $154.70  
  Purchase #7 $225.70   3.285%   $233.1142   $233.11   $233.10   $233.10  
  7 purchase totals = $1,071.98       $1,142.2626   $1,142.27   $1,142.30   $1,142.30