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 $126.43   11.531%   $141.0086   $141.01   $141.00   $141.00  
  Purchase #2 $67.58   9.659%   $74.1076   $74.11   $74.10   $74.10  
  Purchase #3 $113.74   7.400%   $122.1568   $122.16   $122.15   $122.20  
  Purchase #4 $174.29   7.810%   $187.902   $187.90   $187.90   $187.90  
  Purchase #5 $224.53   4.447%   $234.5148   $234.51   $234.50   $234.50  
  Purchase #6 $215.58   13.787%   $245.302   $245.30   $245.30   $245.30  
  Purchase #7 $109.92   7.637%   $118.3146   $118.31   $118.30   $118.30  
  7 purchase totals = $1,032.07       $1,123.3064   $1,123.30   $1,123.25   $1,123.30