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	$135.63	11.575%	$151.3292	$151.33	$151.35	$151.30
Purchase #2	$230.27	5.362%	$242.6171	$242.62	$242.60	$242.60
Purchase #3	$214.68	11.197%	$238.7177	$238.72	$238.70	$238.70
Purchase #4	$78.62	11.436%	$87.611	$87.61	$87.60	$87.60
Purchase #5	$142.86	13.744%	$162.4947	$162.49	$162.50	$162.50
Purchase #6	$68.83	11.606%	$76.8184	$76.82	$76.80	$76.80
Purchase #7	$145.30	5.515%	$153.3133	$153.31	$153.30	$153.30
7 purchase totals =	$1,016.19		$1,112.9014	$1,112.90	$1,112.85	$1,112.80