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	$35.51	6.275%	$37.7383	$37.74	$37.75	$37.70
Purchase #2	$116.67	9.428%	$127.6696	$127.67	$127.65	$127.70
Purchase #3	$160.60	8.152%	$173.6921	$173.69	$173.70	$173.70
Purchase #4	$235.71	4.132%	$245.4495	$245.45	$245.45	$245.40
Purchase #5	$136.75	5.263%	$143.9472	$143.95	$143.95	$143.90
Purchase #6	$11.36	6.290%	$12.0745	$12.07	$12.05	$12.10
Purchase #7	$242.91	11.851%	$271.6973	$271.70	$271.70	$271.70
7 purchase totals =	$939.51		$1,012.2685	$1,012.27	$1,012.25	$1,012.20