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 $168.55   8.127%   $182.2481   $182.25   $182.25   $182.20  
  Purchase #2 $247.62   6.867%   $264.6241   $264.62   $264.60   $264.60  
  Purchase #3 $243.32   11.446%   $271.1704   $271.17   $271.15   $271.20  
  Purchase #4 $88.62   7.721%   $95.4624   $95.46   $95.45   $95.50  
  Purchase #5 $197.35   10.379%   $217.833   $217.83   $217.85   $217.80  
  Purchase #6 $176.93   10.658%   $195.7872   $195.79   $195.80   $195.80  
  Purchase #7 $250.50   5.123%   $263.3331   $263.33   $263.35   $263.30  
  7 purchase totals = $1,372.89       $1,490.4583   $1,490.45   $1,490.45   $1,490.40