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	$209.56	11.304%	$233.2487	$233.25	$233.25	$233.20
Purchase #2	$105.74	11.606%	$118.0122	$118.01	$118.00	$118.00
Purchase #3	$152.94	13.599%	$173.7383	$173.74	$173.75	$173.70
Purchase #4	$9.94	4.362%	$10.3736	$10.37	$10.35	$10.40
Purchase #5	$200.39	6.760%	$213.9364	$213.94	$213.95	$213.90
Purchase #6	$118.68	7.532%	$127.619	$127.62	$127.60	$127.60
Purchase #7	$45.88	3.743%	$47.5973	$47.60	$47.60	$47.60
7 purchase totals =	$843.13		$924.5255	$924.53	$924.50	$924.40