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	$207.93	4.244%	$216.7545	$216.75	$216.75	$216.80
Purchase #2	$178.82	3.142%	$184.4385	$184.44	$184.45	$184.40
Purchase #3	$69.46	10.696%	$76.8894	$76.89	$76.90	$76.90
Purchase #4	$153.69	7.705%	$165.5318	$165.53	$165.55	$165.50
Purchase #5	$83.38	8.370%	$90.3589	$90.36	$90.35	$90.40
Purchase #6	$43.25	4.346%	$45.1296	$45.13	$45.15	$45.10
Purchase #7	$229.72	4.769%	$240.6753	$240.68	$240.70	$240.70
7 purchase totals =	$966.25		$1,019.7780	$1,019.78	$1,019.85	$1,019.80