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   6.350%   $71.7331   $71.73   $71.75   $71.70  
  Purchase #2 $213.45   4.790%   $223.6743   $223.67   $223.65   $223.70  
  Purchase #3 $71.74   3.544%   $74.2825   $74.28   $74.30   $74.30  
  Purchase #4 $23.96   9.419%   $26.2168   $26.22   $26.20   $26.20  
  Purchase #5 $188.36   6.447%   $200.5036   $200.50   $200.50   $200.50  
  Purchase #6 $59.32   5.180%   $62.3928   $62.39   $62.40   $62.40  
  Purchase #7 $192.92   11.243%   $214.61   $214.61   $214.60   $214.60  
  7 purchase totals = $817.20       $873.4131   $873.40   $873.40   $873.40