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	$47.69	3.857%	$49.5294	$49.53	$49.55	$49.50
Purchase #2	$59.71	5.178%	$62.8018	$62.80	$62.80	$62.80
Purchase #3	$131.72	11.295%	$146.5978	$146.60	$146.60	$146.60
Purchase #4	$153.69	10.818%	$170.3162	$170.32	$170.30	$170.30
Purchase #5	$143.57	6.203%	$152.4756	$152.48	$152.50	$152.50
Purchase #6	$247.79	11.137%	$275.3864	$275.39	$275.40	$275.40
Purchase #7	$221.54	6.551%	$236.0531	$236.05	$236.05	$236.10
7 purchase totals =	$1,005.71		$1,093.1603	$1,093.17	$1,093.20	$1,093.20