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 $210.40   10.599%   $232.7003   $232.70   $232.70   $232.70  
  Purchase #2 $115.63   3.322%   $119.4712   $119.47   $119.45   $119.50  
  Purchase #3 $178.27   3.530%   $184.5629   $184.56   $184.55   $184.60  
  Purchase #4 $235.73   5.452%   $248.582   $248.58   $248.60   $248.60  
  Purchase #5 $156.37   13.740%   $177.8552   $177.86   $177.85   $177.90  
  Purchase #6 $30.65   4.804%   $32.1224   $32.12   $32.10   $32.10  
  Purchase #7 $16.90   13.668%   $19.2099   $19.21   $19.20   $19.20  
  7 purchase totals = $943.95       $1,014.5039   $1,014.50   $1,014.45   $1,014.60