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	$124.51	4.488%	$130.098	$130.10	$130.10	$130.10
Purchase #2	$76.73	9.278%	$83.849	$83.85	$83.85	$83.80
Purchase #3	$24.69	13.556%	$28.037	$28.04	$28.05	$28.00
Purchase #4	$70.84	9.663%	$77.6853	$77.69	$77.70	$77.70
Purchase #5	$247.81	3.156%	$255.6309	$255.63	$255.65	$255.60
Purchase #6	$43.69	3.287%	$45.1261	$45.13	$45.15	$45.10
Purchase #7	$235.27	6.177%	$249.8026	$249.80	$249.80	$249.80
7 purchase totals =	$823.54		$870.2289	$870.24	$870.30	$870.10