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	$70.87	4.203%	$73.8487	$73.85	$73.85	$73.80
Purchase #2	$6.44	10.333%	$7.1054	$7.11	$7.10	$7.10
Purchase #3	$58.91	5.475%	$62.1353	$62.14	$62.15	$62.10
Purchase #4	$146.80	3.516%	$151.9615	$151.96	$151.95	$152.00
Purchase #5	$139.97	13.491%	$158.8534	$158.85	$158.85	$158.90
Purchase #6	$157.35	9.614%	$172.4776	$172.48	$172.50	$172.50
Purchase #7	$59.48	13.153%	$67.3034	$67.30	$67.30	$67.30
7 purchase totals =	$639.82		$693.6853	$693.69	$693.70	$693.70