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	$10.83	7.617%	$11.6549	$11.65	$11.65	$11.70
Purchase #2	$98.88	13.263%	$111.9945	$111.99	$112.00	$112.00
Purchase #3	$10.39	7.553%	$11.1748	$11.17	$11.15	$11.20
Purchase #4	$160.78	7.823%	$173.3578	$173.36	$173.35	$173.40
Purchase #5	$159.34	6.636%	$169.9138	$169.91	$169.90	$169.90
Purchase #6	$55.90	3.676%	$57.9549	$57.95	$57.95	$58.00
Purchase #7	$145.38	4.846%	$152.4251	$152.43	$152.45	$152.40
7 purchase totals =	$641.50		$688.4758	$688.46	$688.45	$688.60