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 $209.51   11.672%   $233.964   $233.96   $233.95   $234.00  
  Purchase #2 $92.33   7.821%   $99.5511   $99.55   $99.55   $99.60  
  Purchase #3 $44.31   9.256%   $48.4113   $48.41   $48.40   $48.40  
  Purchase #4 $210.34   4.587%   $219.9883   $219.99   $220.00   $220.00  
  Purchase #5 $81.99   4.178%   $85.4155   $85.42   $85.40   $85.40  
  Purchase #6 $195.65   4.762%   $204.9669   $204.97   $204.95   $205.00  
  Purchase #7 $115.68   8.590%   $125.6169   $125.62   $125.60   $125.60  
  7 purchase totals = $949.81       $1,017.9140   $1,017.92   $1,017.85   $1,018.00