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	$62.30	4.197%	$64.9147	$64.91	$64.90	$64.90
Purchase #2	$158.66	4.282%	$165.4538	$165.45	$165.45	$165.50
Purchase #3	$242.59	12.538%	$273.0059	$273.01	$273.00	$273.00
Purchase #4	$53.99	3.613%	$55.9407	$55.94	$55.95	$55.90
Purchase #5	$192.43	9.447%	$210.6089	$210.61	$210.60	$210.60
Purchase #6	$181.27	8.417%	$196.5275	$196.53	$196.55	$196.50
Purchase #7	$30.57	11.844%	$34.1907	$34.19	$34.20	$34.20
7 purchase totals =	$921.81		$1,000.6422	$1,000.64	$1,000.65	$1,000.60