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 $95.61   12.572%   $107.6301   $107.63   $107.65   $107.60  
  Purchase #2 $163.97   12.797%   $184.9532   $184.95   $184.95   $185.00  
  Purchase #3 $161.25   9.215%   $176.1092   $176.11   $176.10   $176.10  
  Purchase #4 $36.69   9.218%   $40.0721   $40.07   $40.05   $40.10  
  Purchase #5 $202.71   10.639%   $224.2763   $224.28   $224.30   $224.30  
  Purchase #6 $204.63   12.456%   $230.1187   $230.12   $230.10   $230.10  
  Purchase #7 $82.82   10.782%   $91.7497   $91.75   $91.75   $91.70  
  7 purchase totals = $947.68       $1,054.9093   $1,054.91   $1,054.90   $1,054.90