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 $83.62   13.605%   $94.9965   $95.00   $95.00   $95.00  
  Purchase #2 $37.38   5.295%   $39.3593   $39.36   $39.35   $39.40  
  Purchase #3 $112.76   9.157%   $123.0854   $123.09   $123.10   $123.10  
  Purchase #4 $149.62   13.279%   $169.488   $169.49   $169.50   $169.50  
  Purchase #5 $120.79   11.871%   $135.129   $135.13   $135.15   $135.10  
  Purchase #6 $138.61   4.190%   $144.4178   $144.42   $144.40   $144.40  
  Purchase #7 $173.66   7.195%   $186.1548   $186.15   $186.15   $186.20  
  7 purchase totals = $816.44       $892.6308   $892.64   $892.65   $892.70