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	$96.36	9.343%	$105.3629	$105.36	$105.35	$105.40
Purchase #2	$92.45	4.566%	$96.6713	$96.67	$96.65	$96.70
Purchase #3	$121.96	4.296%	$127.1994	$127.20	$127.20	$127.20
Purchase #4	$197.86	13.483%	$224.5375	$224.54	$224.55	$224.50
Purchase #5	$35.91	6.733%	$38.3278	$38.33	$38.35	$38.30
Purchase #6	$118.83	10.788%	$131.6494	$131.65	$131.65	$131.60
Purchase #7	$31.76	11.837%	$35.5194	$35.52	$35.50	$35.50
7 purchase totals =	$695.13		$759.2677	$759.27	$759.25	$759.20