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 $147.38   5.591%   $155.62   $155.62   $155.60   $155.60  
  Purchase #2 $83.92   4.863%   $88.001   $88.00   $88.00   $88.00  
  Purchase #3 $219.47   11.281%   $244.2284   $244.23   $244.25   $244.20  
  Purchase #4 $153.42   4.695%   $160.6231   $160.62   $160.60   $160.60  
  Purchase #5 $192.42   7.378%   $206.6167   $206.62   $206.60   $206.60  
  Purchase #6 $217.34   4.349%   $226.7921   $226.79   $226.80   $226.80  
  Purchase #7 $95.30   5.592%   $100.6292   $100.63   $100.65   $100.60  
  7 purchase totals = $1,109.25       $1,182.5105   $1,182.51   $1,182.50   $1,182.40