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	$98.39	7.240%	$105.5134	$105.51	$105.50	$105.50
Purchase #2	$52.91	6.142%	$56.1597	$56.16	$56.15	$56.20
Purchase #3	$27.86	9.667%	$30.5532	$30.55	$30.55	$30.60
Purchase #4	$142.76	11.708%	$159.4743	$159.47	$159.45	$159.50
Purchase #5	$57.83	6.531%	$61.6069	$61.61	$61.60	$61.60
Purchase #6	$46.49	13.280%	$52.6639	$52.66	$52.65	$52.70
Purchase #7	$152.87	3.194%	$157.7527	$157.75	$157.75	$157.80
7 purchase totals =	$579.11		$623.7241	$623.71	$623.65	$623.90