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 $67.45   9.765%   $74.0365   $74.04   $74.05   $74.00  
  Purchase #2 $205.46   7.862%   $221.6133   $221.61   $221.60   $221.60  
  Purchase #3 $246.30   13.475%   $279.4889   $279.49   $279.50   $279.50  
  Purchase #4 $203.52   5.128%   $213.9565   $213.96   $213.95   $214.00  
  Purchase #5 $159.60   6.680%   $170.2613   $170.26   $170.25   $170.30  
  Purchase #6 $172.98   5.542%   $182.5666   $182.57   $182.55   $182.60  
  Purchase #7 $119.50   8.195%   $129.293   $129.29   $129.30   $129.30  
  7 purchase totals = $1,174.81       $1,271.2161   $1,271.22   $1,271.20   $1,271.30