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 $177.82   13.352%   $201.5625   $201.56   $201.55   $201.60  
  Purchase #2 $194.27   9.823%   $213.3531   $213.35   $213.35   $213.40  
  Purchase #3 $65.86   4.494%   $68.8197   $68.82   $68.80   $68.80  
  Purchase #4 $139.56   9.741%   $153.1545   $153.15   $153.15   $153.20  
  Purchase #5 $168.67   7.778%   $181.7892   $181.79   $181.80   $181.80  
  Purchase #6 $21.48   4.282%   $22.3998   $22.40   $22.40   $22.40  
  Purchase #7 $194.93   5.801%   $206.2379   $206.24   $206.25   $206.20  
  7 purchase totals = $962.59       $1,047.3167   $1,047.31   $1,047.30   $1,047.40