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 $225.67   4.261%   $235.2858   $235.29   $235.30   $235.30  
  Purchase #2 $162.95   4.114%   $169.6538   $169.65   $169.65   $169.70  
  Purchase #3 $24.47   6.733%   $26.1176   $26.12   $26.10   $26.10  
  Purchase #4 $146.96   10.168%   $161.9029   $161.90   $161.90   $161.90  
  Purchase #5 $128.65   6.849%   $137.4612   $137.46   $137.45   $137.50  
  Purchase #6 $213.75   4.780%   $223.9673   $223.97   $223.95   $224.00  
  Purchase #7 $132.64   11.807%   $148.3008   $148.30   $148.30   $148.30  
  7 purchase totals = $1,035.09       $1,102.6894   $1,102.69   $1,102.65   $1,102.80