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 $177.45   13.496%   $201.3987   $201.40   $201.40   $201.40  
  Purchase #2 $230.88   13.657%   $262.4113   $262.41   $262.40   $262.40  
  Purchase #3 $47.41   3.557%   $49.0964   $49.10   $49.10   $49.10  
  Purchase #4 $101.56   3.135%   $104.7439   $104.74   $104.75   $104.70  
  Purchase #5 $138.74   10.456%   $153.2467   $153.25   $153.25   $153.20  
  Purchase #6 $210.97   10.692%   $233.5269   $233.53   $233.55   $233.50  
  Purchase #7 $53.60   4.204%   $55.8533   $55.85   $55.85   $55.90  
  7 purchase totals = $960.61       $1,060.2772   $1,060.28   $1,060.30   $1,060.20