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	$20.79	8.130%	$22.4802	$22.48	$22.50	$22.50
Purchase #2	$167.44	10.863%	$185.629	$185.63	$185.65	$185.60
Purchase #3	$65.67	10.347%	$72.4649	$72.46	$72.45	$72.50
Purchase #4	$106.92	4.707%	$111.9527	$111.95	$111.95	$112.00
Purchase #5	$67.99	9.451%	$74.4157	$74.42	$74.40	$74.40
Purchase #6	$70.89	12.682%	$79.8803	$79.88	$79.90	$79.90
Purchase #7	$149.50	4.634%	$156.4278	$156.43	$156.45	$156.40
7 purchase totals =	$649.20		$703.2506	$703.25	$703.30	$703.30