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 $213.63   8.222%   $231.1947   $231.19   $231.20   $231.20  
  Purchase #2 $48.93   5.438%   $51.5908   $51.59   $51.60   $51.60  
  Purchase #3 $64.65   4.356%   $67.4662   $67.47   $67.45   $67.50  
  Purchase #4 $246.26   9.418%   $269.4528   $269.45   $269.45   $269.50  
  Purchase #5 $59.35   9.383%   $64.9188   $64.92   $64.90   $64.90  
  Purchase #6 $230.64   4.770%   $241.6415   $241.64   $241.65   $241.60  
  Purchase #7 $98.53   7.417%   $105.838   $105.84   $105.85   $105.80  
  7 purchase totals = $961.99       $1,032.1028   $1,032.10   $1,032.10   $1,032.10