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 $182.59   6.792%   $194.9915   $194.99   $195.00   $195.00  
  Purchase #2 $42.61   6.460%   $45.3626   $45.36   $45.35   $45.40  
  Purchase #3 $245.87   8.711%   $267.2877   $267.29   $267.30   $267.30  
  Purchase #4 $250.76   12.104%   $281.112   $281.11   $281.10   $281.10  
  Purchase #5 $24.78   3.570%   $25.6646   $25.66   $25.65   $25.70  
  Purchase #6 $129.40   12.717%   $145.8558   $145.86   $145.85   $145.90  
  Purchase #7 $141.65   6.600%   $150.9989   $151.00   $151.00   $151.00  
  7 purchase totals = $1,017.66       $1,111.2731   $1,111.27   $1,111.25   $1,111.40