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 $140.93   9.733%   $154.6467   $154.65   $154.65   $154.60  
  Purchase #2 $181.98   6.780%   $194.3182   $194.32   $194.30   $194.30  
  Purchase #3 $146.88   8.374%   $159.1797   $159.18   $159.20   $159.20  
  Purchase #4 $229.99   7.229%   $246.616   $246.62   $246.60   $246.60  
  Purchase #5 $103.71   11.311%   $115.4406   $115.44   $115.45   $115.40  
  Purchase #6 $10.58   9.122%   $11.5451   $11.55   $11.55   $11.50  
  Purchase #7 $146.41   4.792%   $153.426   $153.43   $153.45   $153.40  
  7 purchase totals = $960.48       $1,035.1723   $1,035.19   $1,035.20   $1,035.00