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 $32.76   6.166%   $34.78   $34.78   $34.80   $34.80  
  Purchase #2 $212.52   10.274%   $234.3543   $234.35   $234.35   $234.40  
  Purchase #3 $29.98   4.522%   $31.3357   $31.34   $31.35   $31.30  
  Purchase #4 $165.29   6.600%   $176.1991   $176.20   $176.20   $176.20  
  Purchase #5 $197.60   10.506%   $218.3599   $218.36   $218.35   $218.40  
  Purchase #6 $118.64   5.651%   $125.3443   $125.34   $125.35   $125.30  
  Purchase #7 $199.40   12.530%   $224.3848   $224.38   $224.40   $224.40  
  7 purchase totals = $956.19       $1,044.7581   $1,044.75   $1,044.80   $1,044.80