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 $72.79   4.571%   $76.1172   $76.12   $76.10   $76.10  
  Purchase #2 $250.86   8.470%   $272.1078   $272.11   $272.10   $272.10  
  Purchase #3 $152.47   9.693%   $167.2489   $167.25   $167.25   $167.20  
  Purchase #4 $145.55   10.750%   $161.1966   $161.20   $161.20   $161.20  
  Purchase #5 $82.60   5.807%   $87.3966   $87.40   $87.40   $87.40  
  Purchase #6 $154.50   4.813%   $161.9361   $161.94   $161.95   $161.90  
  Purchase #7 $250.34   7.750%   $269.7414   $269.74   $269.75   $269.70  
  7 purchase totals = $1,109.11       $1,195.7446   $1,195.76   $1,195.75   $1,195.60