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	$176.96	7.398%	$190.0515	$190.05	$190.05	$190.10
Purchase #2	$193.68	12.278%	$217.46	$217.46	$217.45	$217.50
Purchase #3	$36.79	12.301%	$41.3155	$41.32	$41.30	$41.30
Purchase #4	$135.37	10.850%	$150.0576	$150.06	$150.05	$150.10
Purchase #5	$18.42	5.558%	$19.4438	$19.44	$19.45	$19.40
Purchase #6	$226.77	12.144%	$254.3089	$254.31	$254.30	$254.30
Purchase #7	$171.94	10.802%	$190.513	$190.51	$190.50	$190.50
7 purchase totals =	$959.93		$1,063.1503	$1,063.15	$1,063.10	$1,063.20