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 $62.26   7.632%   $67.0117   $67.01   $67.00   $67.00  
  Purchase #2 $41.76   9.462%   $45.7113   $45.71   $45.70   $45.70  
  Purchase #3 $202.43   7.587%   $217.7884   $217.79   $217.80   $217.80  
  Purchase #4 $94.73   4.816%   $99.2922   $99.29   $99.30   $99.30  
  Purchase #5 $207.65   8.147%   $224.5672   $224.57   $224.55   $224.60  
  Purchase #6 $93.75   3.284%   $96.8288   $96.83   $96.85   $96.80  
  Purchase #7 $118.87   4.436%   $124.1431   $124.14   $124.15   $124.10  
  7 purchase totals = $821.45       $875.3427   $875.34   $875.35   $875.30