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 $192.98   4.749%   $202.1446   $202.14   $202.15   $202.10  
  Purchase #2 $196.81   3.453%   $203.6058   $203.61   $203.60   $203.60  
  Purchase #3 $185.77   11.859%   $207.8005   $207.80   $207.80   $207.80  
  Purchase #4 $249.52   7.667%   $268.6507   $268.65   $268.65   $268.70  
  Purchase #5 $127.94   6.239%   $135.9222   $135.92   $135.90   $135.90  
  Purchase #6 $243.74   9.532%   $266.9733   $266.97   $266.95   $267.00  
  Purchase #7 $19.29   11.593%   $21.5263   $21.53   $21.55   $21.50  
  7 purchase totals = $1,216.05       $1,306.6234   $1,306.62   $1,306.60   $1,306.60