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	$160.63	11.563%	$179.2036	$179.20	$179.20	$179.20
Purchase #2	$188.43	8.409%	$204.2751	$204.28	$204.30	$204.30
Purchase #3	$130.85	8.621%	$142.1306	$142.13	$142.15	$142.10
Purchase #4	$45.31	6.567%	$48.2855	$48.29	$48.30	$48.30
Purchase #5	$55.48	7.522%	$59.6532	$59.65	$59.65	$59.70
Purchase #6	$43.25	5.700%	$45.7153	$45.72	$45.70	$45.70
Purchase #7	$50.67	7.319%	$54.3785	$54.38	$54.40	$54.40
7 purchase totals =	$674.62		$733.6418	$733.65	$733.70	$733.70