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 $146.98   3.650%   $152.3448   $152.34   $152.35   $152.30  
  Purchase #2 $43.62   5.652%   $46.0854   $46.09   $46.10   $46.10  
  Purchase #3 $165.42   10.739%   $183.1845   $183.18   $183.20   $183.20  
  Purchase #4 $63.59   3.382%   $65.7406   $65.74   $65.75   $65.70  
  Purchase #5 $132.59   9.436%   $145.1012   $145.10   $145.10   $145.10  
  Purchase #6 $60.46   3.201%   $62.3953   $62.40   $62.40   $62.40  
  Purchase #7 $99.68   11.331%   $110.9747   $110.97   $110.95   $111.00  
  7 purchase totals = $712.34       $765.8265   $765.82   $765.85   $765.80