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 $93.85   3.496%   $97.131   $97.13   $97.15   $97.10  
  Purchase #2 $148.67   13.135%   $168.1978   $168.20   $168.20   $168.20  
  Purchase #3 $250.95   9.257%   $274.1804   $274.18   $274.20   $274.20  
  Purchase #4 $102.89   12.753%   $116.0116   $116.01   $116.00   $116.00  
  Purchase #5 $158.84   6.111%   $168.5467   $168.55   $168.55   $168.50  
  Purchase #6 $138.37   7.346%   $148.5347   $148.53   $148.55   $148.50  
  Purchase #7 $57.41   11.437%   $63.976   $63.98   $64.00   $64.00  
  7 purchase totals = $950.98       $1,036.5782   $1,036.58   $1,036.65   $1,036.50