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 $62.48   4.603%   $65.356   $65.36   $65.35   $65.40  
  Purchase #2 $215.49   8.559%   $233.9338   $233.93   $233.95   $233.90  
  Purchase #3 $148.50   8.718%   $161.4462   $161.45   $161.45   $161.40  
  Purchase #4 $213.39   6.534%   $227.3329   $227.33   $227.35   $227.30  
  Purchase #5 $36.27   9.658%   $39.773   $39.77   $39.75   $39.80  
  Purchase #6 $116.54   10.643%   $128.9434   $128.94   $128.95   $128.90  
  Purchase #7 $148.42   6.107%   $157.484   $157.48   $157.50   $157.50  
  7 purchase totals = $941.09       $1,014.2693   $1,014.26   $1,014.30   $1,014.20