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 $66.26   11.225%   $73.6977   $73.70   $73.70   $73.70  
  Purchase #2 $232.50   4.489%   $242.9369   $242.94   $242.95   $242.90  
  Purchase #3 $214.65   5.133%   $225.668   $225.67   $225.65   $225.70  
  Purchase #4 $154.29   3.156%   $159.1594   $159.16   $159.15   $159.20  
  Purchase #5 $235.73   13.628%   $267.8553   $267.86   $267.85   $267.90  
  Purchase #6 $94.28   6.777%   $100.6694   $100.67   $100.65   $100.70  
  Purchase #7 $58.87   6.422%   $62.6506   $62.65   $62.65   $62.70  
  7 purchase totals = $1,056.58       $1,132.6373   $1,132.65   $1,132.60   $1,132.80