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 $124.52   7.619%   $134.0072   $134.01   $134.00   $134.00  
  Purchase #2 $217.71   8.310%   $235.8017   $235.80   $235.80   $235.80  
  Purchase #3 $98.35   12.184%   $110.333   $110.33   $110.35   $110.30  
  Purchase #4 $222.69   5.309%   $234.5126   $234.51   $234.50   $234.50  
  Purchase #5 $58.67   6.680%   $62.5892   $62.59   $62.60   $62.60  
  Purchase #6 $195.38   8.747%   $212.4699   $212.47   $212.45   $212.50  
  Purchase #7 $175.73   10.654%   $194.4523   $194.45   $194.45   $194.50  
  7 purchase totals = $1,093.05       $1,184.1659   $1,184.16   $1,184.15   $1,184.20