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	$208.49	13.613%	$236.8717	$236.87	$236.85	$236.90
Purchase #2	$25.91	7.575%	$27.8727	$27.87	$27.85	$27.90
Purchase #3	$50.48	13.706%	$57.3988	$57.40	$57.40	$57.40
Purchase #4	$162.86	13.700%	$185.1718	$185.17	$185.15	$185.20
Purchase #5	$143.60	11.384%	$159.9474	$159.95	$159.95	$159.90
Purchase #6	$187.87	12.133%	$210.6643	$210.66	$210.65	$210.70
Purchase #7	$244.47	8.148%	$264.3894	$264.39	$264.40	$264.40
7 purchase totals =	$1,023.68		$1,142.3161	$1,142.31	$1,142.25	$1,142.40