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	$175.93	11.388%	$195.9649	$195.96	$195.95	$196.00
Purchase #2	$87.56	4.820%	$91.7804	$91.78	$91.80	$91.80
Purchase #3	$45.60	10.726%	$50.4911	$50.49	$50.50	$50.50
Purchase #4	$98.51	13.472%	$111.7813	$111.78	$111.80	$111.80
Purchase #5	$49.31	4.503%	$51.5304	$51.53	$51.55	$51.50
Purchase #6	$48.62	11.198%	$54.0645	$54.06	$54.05	$54.10
Purchase #7	$247.80	4.364%	$258.614	$258.61	$258.60	$258.60
7 purchase totals =	$753.33		$814.2266	$814.21	$814.25	$814.30