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 $61.28   12.655%   $69.035   $69.04   $69.05   $69.00  
  Purchase #2 $192.61   9.812%   $211.5089   $211.51   $211.50   $211.50  
  Purchase #3 $195.72   10.339%   $215.9555   $215.96   $215.95   $216.00  
  Purchase #4 $177.82   7.580%   $191.2988   $191.30   $191.30   $191.30  
  Purchase #5 $205.55   12.462%   $231.1656   $231.17   $231.15   $231.20  
  Purchase #6 $56.86   12.800%   $64.1381   $64.14   $64.15   $64.10  
  Purchase #7 $144.49   11.410%   $160.9763   $160.98   $161.00   $161.00  
  7 purchase totals = $1,034.33       $1,144.0782   $1,144.10   $1,144.10   $1,144.10