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	$171.70	11.807%	$191.9726	$191.97	$191.95	$192.00
Purchase #2	$64.83	3.263%	$66.9454	$66.95	$66.95	$66.90
Purchase #3	$96.87	7.532%	$104.1662	$104.17	$104.15	$104.20
Purchase #4	$219.72	9.772%	$241.191	$241.19	$241.20	$241.20
Purchase #5	$29.60	8.580%	$32.1397	$32.14	$32.15	$32.10
Purchase #6	$53.55	10.421%	$59.1304	$59.13	$59.15	$59.10
Purchase #7	$127.75	8.740%	$138.9154	$138.92	$138.90	$138.90
7 purchase totals =	$764.02		$834.4607	$834.47	$834.45	$834.40