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	$199.28	3.335%	$205.926	$205.93	$205.95	$205.90
Purchase #2	$241.62	13.872%	$275.1375	$275.14	$275.15	$275.10
Purchase #3	$109.59	11.508%	$122.2016	$122.20	$122.20	$122.20
Purchase #4	$139.48	12.466%	$156.8676	$156.87	$156.85	$156.90
Purchase #5	$54.25	9.518%	$59.4135	$59.41	$59.40	$59.40
Purchase #6	$195.31	4.818%	$204.72	$204.72	$204.70	$204.70
Purchase #7	$18.85	12.242%	$21.1576	$21.16	$21.15	$21.20
7 purchase totals =	$958.38		$1,045.4238	$1,045.43	$1,045.40	$1,045.40