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	$217.75	11.519%	$242.8326	$242.83	$242.85	$242.80
Purchase #2	$131.25	6.749%	$140.1081	$140.11	$140.10	$140.10
Purchase #3	$86.57	5.537%	$91.3634	$91.36	$91.35	$91.40
Purchase #4	$164.69	5.629%	$173.9604	$173.96	$173.95	$174.00
Purchase #5	$34.75	8.111%	$37.5686	$37.57	$37.55	$37.60
Purchase #6	$100.29	11.498%	$111.8213	$111.82	$111.80	$111.80
Purchase #7	$50.65	5.466%	$53.4185	$53.42	$53.40	$53.40
7 purchase totals =	$785.95		$851.0729	$851.07	$851.00	$851.10