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 $119.25   6.147%   $126.5803   $126.58   $126.60   $126.60  
  Purchase #2 $118.56   9.286%   $129.5695   $129.57   $129.55   $129.60  
  Purchase #3 $95.76   11.190%   $106.4755   $106.48   $106.50   $106.50  
  Purchase #4 $106.39   11.273%   $118.3833   $118.38   $118.40   $118.40  
  Purchase #5 $92.82   9.119%   $101.2843   $101.28   $101.30   $101.30  
  Purchase #6 $158.96   9.215%   $173.6082   $173.61   $173.60   $173.60  
  Purchase #7 $89.40   8.511%   $97.0088   $97.01   $97.00   $97.00  
  7 purchase totals = $781.14       $852.9099   $852.91   $852.95   $853.00