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 $175.84   10.693%   $194.6426   $194.64   $194.65   $194.60  
  Purchase #2 $119.52   4.779%   $125.2319   $125.23   $125.25   $125.20  
  Purchase #3 $87.86   7.501%   $94.4504   $94.45   $94.45   $94.50  
  Purchase #4 $138.65   13.866%   $157.8752   $157.88   $157.90   $157.90  
  Purchase #5 $142.97   4.365%   $149.2106   $149.21   $149.20   $149.20  
  Purchase #6 $163.97   5.502%   $172.9916   $172.99   $173.00   $173.00  
  Purchase #7 $194.98   12.783%   $219.9043   $219.90   $219.90   $219.90  
  7 purchase totals = $1,023.79       $1,114.3066   $1,114.30   $1,114.35   $1,114.30