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 $62.32   10.658%   $68.9621   $68.96   $68.95   $69.00  
  Purchase #2 $132.88   11.197%   $147.7586   $147.76   $147.75   $147.80  
  Purchase #3 $185.29   10.161%   $204.1173   $204.12   $204.10   $204.10  
  Purchase #4 $133.87   11.417%   $149.1539   $149.15   $149.15   $149.20  
  Purchase #5 $77.60   9.399%   $84.8936   $84.89   $84.90   $84.90  
  Purchase #6 $129.55   4.399%   $135.2489   $135.25   $135.25   $135.20  
  Purchase #7 $216.89   9.472%   $237.4338   $237.43   $237.45   $237.40  
  7 purchase totals = $938.40       $1,027.5682   $1,027.56   $1,027.55   $1,027.60