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	$21.84	3.558%	$22.6171	$22.62	$22.60	$22.60
Purchase #2	$73.66	4.361%	$76.8723	$76.87	$76.85	$76.90
Purchase #3	$65.48	9.530%	$71.7202	$71.72	$71.70	$71.70
Purchase #4	$145.48	7.592%	$156.5248	$156.52	$156.50	$156.50
Purchase #5	$241.64	6.109%	$256.4018	$256.40	$256.40	$256.40
Purchase #6	$50.65	5.301%	$53.335	$53.34	$53.35	$53.30
Purchase #7	$12.72	12.473%	$14.3066	$14.31	$14.30	$14.30
7 purchase totals =	$611.47		$651.7778	$651.78	$651.70	$651.70