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 $60.89   10.743%   $67.4314   $67.43   $67.45   $67.40  
  Purchase #2 $221.36   8.836%   $240.9194   $240.92   $240.90   $240.90  
  Purchase #3 $10.49   8.654%   $11.3978   $11.40   $11.40   $11.40  
  Purchase #4 $243.25   5.555%   $256.7625   $256.76   $256.75   $256.80  
  Purchase #5 $7.31   7.427%   $7.8529   $7.85   $7.85   $7.90  
  Purchase #6 $219.43   12.557%   $246.9838   $246.98   $247.00   $247.00  
  Purchase #7 $174.84   4.856%   $183.3302   $183.33   $183.35   $183.30  
  7 purchase totals = $937.57       $1,014.6780   $1,014.67   $1,014.70   $1,014.70