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 $237.41   11.543%   $264.8142   $264.81   $264.80   $264.80  
  Purchase #2 $120.82   3.540%   $125.097   $125.10   $125.10   $125.10  
  Purchase #3 $82.85   11.377%   $92.2758   $92.28   $92.30   $92.30  
  Purchase #4 $30.66   13.687%   $34.8564   $34.86   $34.85   $34.90  
  Purchase #5 $137.98   5.485%   $145.5482   $145.55   $145.55   $145.50  
  Purchase #6 $73.35   13.403%   $83.1811   $83.18   $83.20   $83.20  
  Purchase #7 $19.81   7.296%   $21.2553   $21.26   $21.25   $21.30  
  7 purchase totals = $702.88       $767.0280   $767.04   $767.05   $767.10