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 $194.45   9.396%   $212.7205   $212.72   $212.70   $212.70  
  Purchase #2 $190.36   4.201%   $198.357   $198.36   $198.35   $198.40  
  Purchase #3 $129.79   3.222%   $133.9718   $133.97   $133.95   $134.00  
  Purchase #4 $180.74   9.301%   $197.5506   $197.55   $197.55   $197.60  
  Purchase #5 $139.35   10.873%   $154.5015   $154.50   $154.50   $154.50  
  Purchase #6 $87.71   5.626%   $92.6446   $92.64   $92.65   $92.60  
  Purchase #7 $63.34   11.771%   $70.7958   $70.80   $70.80   $70.80  
  7 purchase totals = $985.74       $1,060.5418   $1,060.54   $1,060.50   $1,060.60