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 $114.61   9.824%   $125.8693   $125.87   $125.85   $125.90  
  Purchase #2 $203.57   6.353%   $216.5028   $216.50   $216.50   $216.50  
  Purchase #3 $115.41   3.143%   $119.0373   $119.04   $119.05   $119.00  
  Purchase #4 $191.66   5.538%   $202.2741   $202.27   $202.25   $202.30  
  Purchase #5 $106.74   13.375%   $121.0165   $121.02   $121.00   $121.00  
  Purchase #6 $216.98   11.817%   $242.6205   $242.62   $242.60   $242.60  
  Purchase #7 $152.52   11.350%   $169.831   $169.83   $169.85   $169.80  
  7 purchase totals = $1,101.49       $1,197.1515   $1,197.15   $1,197.10   $1,197.10