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 $184.65   5.591%   $194.9738   $194.97   $194.95   $195.00  
  Purchase #2 $232.86   10.522%   $257.3615   $257.36   $257.35   $257.40  
  Purchase #3 $26.95   3.651%   $27.9339   $27.93   $27.95   $27.90  
  Purchase #4 $115.73   7.659%   $124.5938   $124.59   $124.60   $124.60  
  Purchase #5 $106.86   3.433%   $110.5285   $110.53   $110.55   $110.50  
  Purchase #6 $112.59   12.325%   $126.4667   $126.47   $126.45   $126.50  
  Purchase #7 $182.55   11.765%   $204.027   $204.03   $204.05   $204.00  
  7 purchase totals = $962.19       $1,045.8852   $1,045.88   $1,045.90   $1,045.90