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	$46.65	11.325%	$51.9331	$51.93	$51.95	$51.90
Purchase #2	$66.29	8.361%	$71.8325	$71.83	$71.85	$71.80
Purchase #3	$36.60	3.772%	$37.9806	$37.98	$38.00	$38.00
Purchase #4	$97.47	9.808%	$107.0299	$107.03	$107.05	$107.00
Purchase #5	$110.80	11.438%	$123.4733	$123.47	$123.45	$123.50
Purchase #6	$56.31	11.658%	$62.8746	$62.87	$62.85	$62.90
Purchase #7	$5.43	8.507%	$5.8919	$5.89	$5.90	$5.90
7 purchase totals =	$419.55		$461.0159	$461.00	$461.05	$461.00