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 $216.26   6.437%   $230.1807   $230.18   $230.20   $230.20  
  Purchase #2 $221.34   11.534%   $246.8694   $246.87   $246.85   $246.90  
  Purchase #3 $87.51   6.519%   $93.2148   $93.21   $93.20   $93.20  
  Purchase #4 $13.70   6.474%   $14.5869   $14.59   $14.60   $14.60  
  Purchase #5 $186.66   5.109%   $196.1965   $196.20   $196.20   $196.20  
  Purchase #6 $46.37   13.144%   $52.4649   $52.46   $52.45   $52.50  
  Purchase #7 $246.95   9.532%   $270.4893   $270.49   $270.50   $270.50  
  7 purchase totals = $1,018.79       $1,104.0025   $1,104.00   $1,104.00   $1,104.10