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 $152.93   13.781%   $174.0053   $174.01   $174.00   $174.00  
  Purchase #2 $97.86   3.763%   $101.5425   $101.54   $101.55   $101.50  
  Purchase #3 $159.85   7.640%   $172.0625   $172.06   $172.05   $172.10  
  Purchase #4 $9.35   3.512%   $9.6784   $9.68   $9.70   $9.70  
  Purchase #5 $244.73   7.783%   $263.7773   $263.78   $263.80   $263.80  
  Purchase #6 $234.36   5.650%   $247.6013   $247.60   $247.60   $247.60  
  Purchase #7 $164.95   11.489%   $183.9011   $183.90   $183.90   $183.90  
  7 purchase totals = $1,064.03       $1,152.5684   $1,152.57   $1,152.60   $1,152.60