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	$223.40	11.105%	$248.2086	$248.21	$248.20	$248.20
Purchase #2	$33.91	4.680%	$35.497	$35.50	$35.50	$35.50
Purchase #3	$241.29	5.232%	$253.9143	$253.91	$253.90	$253.90
Purchase #4	$156.64	10.622%	$173.2783	$173.28	$173.30	$173.30
Purchase #5	$131.27	11.647%	$146.559	$146.56	$146.55	$146.60
Purchase #6	$197.61	6.230%	$209.9211	$209.92	$209.90	$209.90
Purchase #7	$196.93	13.561%	$223.6357	$223.64	$223.65	$223.60
7 purchase totals =	$1,181.05		$1,291.0140	$1,291.02	$1,291.00	$1,291.00