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	$55.85	8.646%	$60.6788	$60.68	$60.70	$60.70
Purchase #2	$27.45	4.595%	$28.7113	$28.71	$28.70	$28.70
Purchase #3	$64.85	4.275%	$67.6223	$67.62	$67.60	$67.60
Purchase #4	$33.89	9.636%	$37.1556	$37.16	$37.15	$37.20
Purchase #5	$200.74	11.130%	$223.0824	$223.08	$223.10	$223.10
Purchase #6	$183.44	6.228%	$194.8646	$194.86	$194.85	$194.90
Purchase #7	$67.88	4.463%	$70.9095	$70.91	$70.90	$70.90
7 purchase totals =	$634.10		$683.0245	$683.02	$683.00	$683.10