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 $187.54   11.832%   $209.7297   $209.73   $209.75   $209.70  
  Purchase #2 $185.25   5.239%   $194.9552   $194.96   $194.95   $195.00  
  Purchase #3 $149.30   12.256%   $167.5982   $167.60   $167.60   $167.60  
  Purchase #4 $195.89   12.574%   $220.5212   $220.52   $220.50   $220.50  
  Purchase #5 $27.29   8.619%   $29.6421   $29.64   $29.65   $29.60  
  Purchase #6 $129.35   13.375%   $146.6506   $146.65   $146.65   $146.70  
  Purchase #7 $119.62   5.214%   $125.857   $125.86   $125.85   $125.90  
  7 purchase totals = $994.24       $1,094.9540   $1,094.96   $1,094.95   $1,095.00