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 $217.28   8.450%   $235.6402   $235.64   $235.65   $235.60  
  Purchase #2 $117.92   6.807%   $125.9468   $125.95   $125.95   $125.90  
  Purchase #3 $62.90   11.188%   $69.9373   $69.94   $69.95   $69.90  
  Purchase #4 $55.46   7.120%   $59.4088   $59.41   $59.40   $59.40  
  Purchase #5 $145.98   10.544%   $161.3721   $161.37   $161.35   $161.40  
  Purchase #6 $136.66   5.212%   $143.7827   $143.78   $143.80   $143.80  
  Purchase #7 $246.90   8.465%   $267.8001   $267.80   $267.80   $267.80  
  7 purchase totals = $983.10       $1,063.8880   $1,063.89   $1,063.90   $1,063.80