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	$216.26	11.271%	$240.6347	$240.63	$240.65	$240.60
Purchase #2	$56.38	6.204%	$59.8778	$59.88	$59.90	$59.90
Purchase #3	$87.99	4.768%	$92.1854	$92.19	$92.20	$92.20
Purchase #4	$88.61	9.201%	$96.763	$96.76	$96.75	$96.80
Purchase #5	$57.83	3.370%	$59.7789	$59.78	$59.80	$59.80
Purchase #6	$77.58	13.613%	$88.141	$88.14	$88.15	$88.10
Purchase #7	$244.89	6.445%	$260.6732	$260.67	$260.65	$260.70
7 purchase totals =	$829.54		$898.0540	$898.05	$898.10	$898.10