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 $87.27   7.629%   $93.9278   $93.93   $93.95   $93.90  
  Purchase #2 $220.70   13.775%   $251.1014   $251.10   $251.10   $251.10  
  Purchase #3 $92.33   3.209%   $95.2929   $95.29   $95.30   $95.30  
  Purchase #4 $110.32   7.432%   $118.519   $118.52   $118.50   $118.50  
  Purchase #5 $242.99   8.480%   $263.5956   $263.60   $263.60   $263.60  
  Purchase #6 $210.92   3.299%   $217.8783   $217.88   $217.90   $217.90  
  Purchase #7 $61.60   10.596%   $68.1271   $68.13   $68.15   $68.10  
  7 purchase totals = $1,026.13       $1,108.4421   $1,108.45   $1,108.50   $1,108.40