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 $43.36   7.590%   $46.651   $46.65   $46.65   $46.70  
  Purchase #2 $106.61   8.525%   $115.6985   $115.70   $115.70   $115.70  
  Purchase #3 $98.63   13.580%   $112.024   $112.02   $112.00   $112.00  
  Purchase #4 $82.36   11.835%   $92.1073   $92.11   $92.10   $92.10  
  Purchase #5 $206.75   6.822%   $220.8545   $220.85   $220.85   $220.90  
  Purchase #6 $199.76   12.400%   $224.5302   $224.53   $224.55   $224.50  
  Purchase #7 $204.48   11.339%   $227.666   $227.67   $227.65   $227.70  
  7 purchase totals = $941.95       $1,039.5315   $1,039.53   $1,039.50   $1,039.60