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	$250.82	6.261%	$266.5238	$266.52	$266.50	$266.50
Purchase #2	$9.78	9.273%	$10.6869	$10.69	$10.70	$10.70
Purchase #3	$6.87	5.699%	$7.2615	$7.26	$7.25	$7.30
Purchase #4	$192.62	13.308%	$218.2539	$218.25	$218.25	$218.30
Purchase #5	$173.56	8.361%	$188.0714	$188.07	$188.05	$188.10
Purchase #6	$86.38	3.299%	$89.2297	$89.23	$89.25	$89.20
Purchase #7	$84.81	13.700%	$96.429	$96.43	$96.45	$96.40
7 purchase totals =	$804.84		$876.4562	$876.45	$876.45	$876.50