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 $167.91   8.604%   $182.357   $182.36   $182.35   $182.40  
  Purchase #2 $215.33   9.270%   $235.2911   $235.29   $235.30   $235.30  
  Purchase #3 $43.64   7.530%   $46.9261   $46.93   $46.95   $46.90  
  Purchase #4 $132.31   13.352%   $149.976   $149.98   $150.00   $150.00  
  Purchase #5 $106.77   9.820%   $117.2548   $117.25   $117.25   $117.30  
  Purchase #6 $97.50   8.181%   $105.4765   $105.48   $105.50   $105.50  
  Purchase #7 $213.92   7.824%   $230.6571   $230.66   $230.65   $230.70  
  7 purchase totals = $977.38       $1,067.9386   $1,067.95   $1,068.00   $1,068.10