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 $72.33   7.236%   $77.5638   $77.56   $77.55   $77.60  
  Purchase #2 $100.98   11.600%   $112.6937   $112.69   $112.70   $112.70  
  Purchase #3 $202.55   4.753%   $212.1772   $212.18   $212.20   $212.20  
  Purchase #4 $127.29   3.266%   $131.4473   $131.45   $131.45   $131.40  
  Purchase #5 $64.95   5.293%   $68.3878   $68.39   $68.40   $68.40  
  Purchase #6 $112.50   12.654%   $126.7358   $126.74   $126.75   $126.70  
  Purchase #7 $22.85   5.856%   $24.1881   $24.19   $24.20   $24.20  
  7 purchase totals = $703.45       $753.1937   $753.20   $753.25   $753.20