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 $204.90   4.753%   $214.6389   $214.64   $214.65   $214.60  
  Purchase #2 $172.69   12.379%   $194.0673   $194.07   $194.05   $194.10  
  Purchase #3 $212.58   8.586%   $230.8321   $230.83   $230.85   $230.80  
  Purchase #4 $56.71   3.169%   $58.5071   $58.51   $58.50   $58.50  
  Purchase #5 $234.67   3.355%   $242.5432   $242.54   $242.55   $242.50  
  Purchase #6 $35.83   8.851%   $39.0013   $39.00   $39.00   $39.00  
  Purchase #7 $213.68   5.385%   $225.1867   $225.19   $225.20   $225.20  
  7 purchase totals = $1,131.06       $1,204.7766   $1,204.78   $1,204.80   $1,204.70