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 $87.82   7.259%   $94.1949   $94.19   $94.20   $94.20  
  Purchase #2 $205.97   7.442%   $221.2983   $221.30   $221.30   $221.30  
  Purchase #3 $32.72   3.679%   $33.9238   $33.92   $33.90   $33.90  
  Purchase #4 $85.93   13.639%   $97.65   $97.65   $97.65   $97.70  
  Purchase #5 $231.98   9.113%   $253.1203   $253.12   $253.10   $253.10  
  Purchase #6 $206.89   13.303%   $234.4126   $234.41   $234.40   $234.40  
  Purchase #7 $153.46   8.854%   $167.0473   $167.05   $167.05   $167.00  
  7 purchase totals = $1,004.77       $1,101.6472   $1,101.64   $1,101.60   $1,101.60