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	$154.27	11.242%	$171.613	$171.61	$171.60	$171.60
Purchase #2	$154.26	11.753%	$172.3902	$172.39	$172.40	$172.40
Purchase #3	$155.66	3.873%	$161.6887	$161.69	$161.70	$161.70
Purchase #4	$218.59	7.519%	$235.0258	$235.03	$235.05	$235.00
Purchase #5	$39.84	9.350%	$43.565	$43.57	$43.55	$43.60
Purchase #6	$100.73	4.689%	$105.4532	$105.45	$105.45	$105.50
Purchase #7	$79.85	4.283%	$83.27	$83.27	$83.25	$83.30
7 purchase totals =	$903.20		$973.0059	$973.01	$973.00	$973.10