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	$173.64	11.231%	$193.1415	$193.14	$193.15	$193.10
Purchase #2	$152.49	8.111%	$164.8585	$164.86	$164.85	$164.90
Purchase #3	$88.89	11.559%	$99.1648	$99.16	$99.15	$99.20
Purchase #4	$236.78	5.372%	$249.4998	$249.50	$249.50	$249.50
Purchase #5	$31.68	12.195%	$35.5434	$35.54	$35.55	$35.50
Purchase #6	$12.61	7.686%	$13.5792	$13.58	$13.60	$13.60
Purchase #7	$120.62	5.642%	$127.4254	$127.43	$127.45	$127.40
7 purchase totals =	$816.71		$883.2126	$883.21	$883.25	$883.20