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	$20.33	8.420%	$22.0418	$22.04	$22.05	$22.00
Purchase #2	$39.80	12.784%	$44.888	$44.89	$44.90	$44.90
Purchase #3	$13.25	10.428%	$14.6317	$14.63	$14.65	$14.60
Purchase #4	$116.56	8.748%	$126.7567	$126.76	$126.75	$126.80
Purchase #5	$91.86	10.111%	$101.148	$101.15	$101.15	$101.10
Purchase #6	$50.48	5.815%	$53.4154	$53.42	$53.40	$53.40
Purchase #7	$53.38	11.823%	$59.6911	$59.69	$59.70	$59.70
7 purchase totals =	$385.66		$422.5727	$422.58	$422.60	$422.50