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 $159.69   11.471%   $178.008   $178.01   $178.00   $178.00  
  Purchase #2 $194.50   8.586%   $211.1998   $211.20   $211.20   $211.20  
  Purchase #3 $67.99   4.700%   $71.1855   $71.19   $71.20   $71.20  
  Purchase #4 $224.31   11.346%   $249.7602   $249.76   $249.75   $249.80  
  Purchase #5 $158.83   12.261%   $178.3041   $178.30   $178.30   $178.30  
  Purchase #6 $87.68   9.604%   $96.1008   $96.10   $96.10   $96.10  
  Purchase #7 $186.25   13.431%   $211.2652   $211.27   $211.25   $211.30  
  7 purchase totals = $1,079.25       $1,195.8236   $1,195.83   $1,195.80   $1,195.90