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 $106.33   6.327%   $113.0575   $113.06   $113.05   $113.10  
  Purchase #2 $219.26   3.323%   $226.546   $226.55   $226.55   $226.50  
  Purchase #3 $119.39   5.636%   $126.1188   $126.12   $126.10   $126.10  
  Purchase #4 $46.96   5.636%   $49.6067   $49.61   $49.60   $49.60  
  Purchase #5 $160.78   5.120%   $169.0119   $169.01   $169.00   $169.00  
  Purchase #6 $46.77   4.867%   $49.0463   $49.05   $49.05   $49.00  
  Purchase #7 $60.88   12.562%   $68.5277   $68.53   $68.55   $68.50  
  7 purchase totals = $760.37       $801.9149   $801.93   $801.90   $801.80