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 $83.34   12.826%   $94.0292   $94.03   $94.05   $94.00  
  Purchase #2 $27.57   6.297%   $29.3061   $29.31   $29.30   $29.30  
  Purchase #3 $63.83   11.458%   $71.1436   $71.14   $71.15   $71.10  
  Purchase #4 $198.93   11.426%   $221.6597   $221.66   $221.65   $221.70  
  Purchase #5 $191.86   7.644%   $206.5258   $206.53   $206.55   $206.50  
  Purchase #6 $200.91   12.797%   $226.6205   $226.62   $226.60   $226.60  
  Purchase #7 $88.88   3.363%   $91.869   $91.87   $91.85   $91.90  
  7 purchase totals = $855.32       $941.1539   $941.16   $941.15   $941.10