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	$202.60	10.625%	$224.1263	$224.13	$224.15	$224.10
Purchase #2	$92.92	11.605%	$103.7034	$103.70	$103.70	$103.70
Purchase #3	$43.38	6.688%	$46.2813	$46.28	$46.30	$46.30
Purchase #4	$230.58	3.593%	$238.8647	$238.86	$238.85	$238.90
Purchase #5	$162.84	10.116%	$179.3129	$179.31	$179.30	$179.30
Purchase #6	$155.74	11.651%	$173.8853	$173.89	$173.90	$173.90
Purchase #7	$133.84	3.742%	$138.8483	$138.85	$138.85	$138.80
7 purchase totals =	$1,021.90		$1,105.0222	$1,105.02	$1,105.05	$1,105.00