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 $181.58   12.408%   $204.1104   $204.11   $204.10   $204.10  
  Purchase #2 $186.94   9.659%   $204.9965   $205.00   $205.00   $205.00  
  Purchase #3 $181.93   12.797%   $205.2116   $205.21   $205.20   $205.20  
  Purchase #4 $238.37   6.502%   $253.8688   $253.87   $253.85   $253.90  
  Purchase #5 $183.97   6.774%   $196.4321   $196.43   $196.45   $196.40  
  Purchase #6 $234.82   3.282%   $242.5268   $242.53   $242.55   $242.50  
  Purchase #7 $54.57   11.706%   $60.958   $60.96   $60.95   $61.00  
  7 purchase totals = $1,262.18       $1,368.1042   $1,368.11   $1,368.10   $1,368.10