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 $59.29   6.186%   $62.9577   $62.96   $62.95   $63.00  
  Purchase #2 $102.32   5.387%   $107.832   $107.83   $107.85   $107.80  
  Purchase #3 $131.98   7.732%   $142.1847   $142.18   $142.20   $142.20  
  Purchase #4 $206.35   4.737%   $216.1248   $216.12   $216.10   $216.10  
  Purchase #5 $64.99   4.143%   $67.6825   $67.68   $67.70   $67.70  
  Purchase #6 $69.48   5.230%   $73.1138   $73.11   $73.10   $73.10  
  Purchase #7 $103.99   12.138%   $116.6123   $116.61   $116.60   $116.60  
  7 purchase totals = $738.40       $786.5078   $786.49   $786.50   $786.50