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	$87.26	4.195%	$90.9206	$90.92	$90.90	$90.90
Purchase #2	$197.52	10.246%	$217.7579	$217.76	$217.75	$217.80
Purchase #3	$135.78	6.381%	$144.4441	$144.44	$144.45	$144.40
Purchase #4	$42.56	4.401%	$44.4331	$44.43	$44.45	$44.40
Purchase #5	$175.64	11.557%	$195.9387	$195.94	$195.95	$195.90
Purchase #6	$234.45	11.787%	$262.0846	$262.08	$262.10	$262.10
Purchase #7	$57.33	7.515%	$61.6383	$61.64	$61.65	$61.60
7 purchase totals =	$930.54		$1,017.2173	$1,017.21	$1,017.25	$1,017.10