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	$190.37	3.173%	$196.4104	$196.41	$196.40	$196.40
Purchase #2	$56.38	10.111%	$62.0806	$62.08	$62.10	$62.10
Purchase #3	$109.58	10.651%	$121.2514	$121.25	$121.25	$121.30
Purchase #4	$69.62	9.192%	$76.0195	$76.02	$76.00	$76.00
Purchase #5	$62.63	4.556%	$65.4834	$65.48	$65.50	$65.50
Purchase #6	$200.94	7.195%	$215.3976	$215.40	$215.40	$215.40
Purchase #7	$41.30	9.858%	$45.3714	$45.37	$45.35	$45.40
7 purchase totals =	$730.82		$782.0143	$782.01	$782.00	$782.10