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 $194.30   3.453%   $201.0092   $201.01   $201.00   $201.00  
  Purchase #2 $32.87   8.714%   $35.7343   $35.73   $35.75   $35.70  
  Purchase #3 $195.76   3.321%   $202.2612   $202.26   $202.25   $202.30  
  Purchase #4 $21.52   3.196%   $22.2078   $22.21   $22.20   $22.20  
  Purchase #5 $99.77   13.524%   $113.2629   $113.26   $113.25   $113.30  
  Purchase #6 $227.46   12.537%   $255.9767   $255.98   $256.00   $256.00  
  Purchase #7 $213.44   8.113%   $230.7564   $230.76   $230.75   $230.80  
  7 purchase totals = $985.12       $1,061.2085   $1,061.21   $1,061.20   $1,061.30