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 $181.59   7.768%   $195.6959   $195.70   $195.70   $195.70  
  Purchase #2 $71.62   5.582%   $75.6178   $75.62   $75.60   $75.60  
  Purchase #3 $232.80   10.192%   $256.527   $256.53   $256.55   $256.50  
  Purchase #4 $17.74   6.655%   $18.9206   $18.92   $18.90   $18.90  
  Purchase #5 $6.32   7.743%   $6.8094   $6.81   $6.80   $6.80  
  Purchase #6 $42.43   4.457%   $44.3211   $44.32   $44.30   $44.30  
  Purchase #7 $160.28   5.341%   $168.8406   $168.84   $168.85   $168.80  
  7 purchase totals = $712.78       $766.7324   $766.74   $766.70   $766.60