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 $67.66   4.346%   $70.6005   $70.60   $70.60   $70.60  
  Purchase #2 $168.88   5.753%   $178.5957   $178.60   $178.60   $178.60  
  Purchase #3 $71.81   5.803%   $75.9771   $75.98   $76.00   $76.00  
  Purchase #4 $91.30   4.265%   $95.1939   $95.19   $95.20   $95.20  
  Purchase #5 $224.96   10.593%   $248.79   $248.79   $248.80   $248.80  
  Purchase #6 $41.89   6.206%   $44.4897   $44.49   $44.50   $44.50  
  Purchase #7 $36.41   4.278%   $37.9676   $37.97   $37.95   $38.00  
  7 purchase totals = $702.91       $751.6145   $751.62   $751.65   $751.70