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 $94.58   11.669%   $105.6165   $105.62   $105.60   $105.60  
  Purchase #2 $152.93   5.259%   $160.9726   $160.97   $160.95   $161.00  
  Purchase #3 $69.59   7.287%   $74.661   $74.66   $74.65   $74.70  
  Purchase #4 $149.27   9.142%   $162.9163   $162.92   $162.90   $162.90  
  Purchase #5 $131.34   5.711%   $138.8408   $138.84   $138.85   $138.80  
  Purchase #6 $52.32   4.814%   $54.8387   $54.84   $54.85   $54.80  
  Purchase #7 $240.86   10.123%   $265.2423   $265.24   $265.25   $265.20  
  7 purchase totals = $890.89       $963.0882   $963.09   $963.05   $963.00