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	$72.58	3.210%	$74.9098	$74.91	$74.90	$74.90
Purchase #2	$54.72	3.843%	$56.8229	$56.82	$56.80	$56.80
Purchase #3	$101.44	9.778%	$111.3588	$111.36	$111.35	$111.40
Purchase #4	$145.93	7.175%	$156.4005	$156.40	$156.40	$156.40
Purchase #5	$224.66	3.716%	$233.0084	$233.01	$233.00	$233.00
Purchase #6	$146.42	6.808%	$156.3883	$156.39	$156.40	$156.40
Purchase #7	$158.38	13.334%	$179.4984	$179.50	$179.50	$179.50
7 purchase totals =	$904.13		$968.3871	$968.39	$968.35	$968.40