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 $65.36   11.142%   $72.6424   $72.64   $72.65   $72.60  
  Purchase #2 $201.54   6.257%   $214.1504   $214.15   $214.15   $214.20  
  Purchase #3 $121.82   7.375%   $130.8042   $130.80   $130.80   $130.80  
  Purchase #4 $115.78   10.871%   $128.3664   $128.37   $128.35   $128.40  
  Purchase #5 $210.60   12.417%   $236.7502   $236.75   $236.75   $236.80  
  Purchase #6 $50.88   5.572%   $53.715   $53.72   $53.70   $53.70  
  Purchase #7 $200.29   9.497%   $219.3115   $219.31   $219.30   $219.30  
  7 purchase totals = $966.27       $1,055.7401   $1,055.74   $1,055.70   $1,055.80