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 $214.50   12.701%   $241.7436   $241.74   $241.75   $241.70  
  Purchase #2 $101.55   4.632%   $106.2538   $106.25   $106.25   $106.30  
  Purchase #3 $21.92   4.813%   $22.975   $22.98   $23.00   $23.00  
  Purchase #4 $180.71   13.180%   $204.5276   $204.53   $204.55   $204.50  
  Purchase #5 $233.97   3.569%   $242.3204   $242.32   $242.30   $242.30  
  Purchase #6 $99.66   6.573%   $106.2107   $106.21   $106.20   $106.20  
  Purchase #7 $205.98   12.792%   $232.329   $232.33   $232.35   $232.30  
  7 purchase totals = $1,058.29       $1,156.3601   $1,156.36   $1,156.40   $1,156.30