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	$136.61	10.207%	$150.5538	$150.55	$150.55	$150.60
Purchase #2	$9.51	10.243%	$10.4841	$10.48	$10.50	$10.50
Purchase #3	$142.95	3.786%	$148.3621	$148.36	$148.35	$148.40
Purchase #4	$104.44	6.471%	$111.1983	$111.20	$111.20	$111.20
Purchase #5	$146.70	3.136%	$151.3005	$151.30	$151.30	$151.30
Purchase #6	$33.43	4.363%	$34.8886	$34.89	$34.90	$34.90
Purchase #7	$222.25	7.808%	$239.6033	$239.60	$239.60	$239.60
7 purchase totals =	$795.89		$846.3907	$846.38	$846.40	$846.50