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 $182.51   6.829%   $194.9736   $194.97   $194.95   $195.00  
  Purchase #2 $109.25   3.587%   $113.1688   $113.17   $113.15   $113.20  
  Purchase #3 $237.37   3.629%   $245.9842   $245.98   $246.00   $246.00  
  Purchase #4 $112.71   12.401%   $126.6872   $126.69   $126.70   $126.70  
  Purchase #5 $94.34   11.315%   $105.0146   $105.01   $105.00   $105.00  
  Purchase #6 $144.77   3.659%   $150.0671   $150.07   $150.05   $150.10  
  Purchase #7 $151.85   4.571%   $158.7911   $158.79   $158.80   $158.80  
  7 purchase totals = $1,032.80       $1,094.6866   $1,094.68   $1,094.65   $1,094.80