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	$145.43	5.841%	$153.9246	$153.92	$153.90	$153.90
Purchase #2	$90.44	4.366%	$94.3886	$94.39	$94.40	$94.40
Purchase #3	$83.87	8.373%	$90.8924	$90.89	$90.90	$90.90
Purchase #4	$233.80	8.173%	$252.9085	$252.91	$252.90	$252.90
Purchase #5	$191.44	5.304%	$201.594	$201.59	$201.60	$201.60
Purchase #6	$176.39	13.672%	$200.506	$200.51	$200.50	$200.50
Purchase #7	$73.29	4.638%	$76.6892	$76.69	$76.70	$76.70
7 purchase totals =	$994.66		$1,070.9033	$1,070.90	$1,070.90	$1,070.90