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	$173.62	9.563%	$190.2233	$190.22	$190.20	$190.20
Purchase #2	$59.70	4.372%	$62.3101	$62.31	$62.30	$62.30
Purchase #3	$195.89	11.674%	$218.7582	$218.76	$218.75	$218.80
Purchase #4	$222.57	11.173%	$247.4377	$247.44	$247.45	$247.40
Purchase #5	$45.35	13.171%	$51.323	$51.32	$51.30	$51.30
Purchase #6	$201.76	7.304%	$216.4966	$216.50	$216.50	$216.50
Purchase #7	$14.81	5.801%	$15.6691	$15.67	$15.65	$15.70
7 purchase totals =	$913.70		$1,002.2180	$1,002.22	$1,002.15	$1,002.20