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	$168.44	12.841%	$190.0694	$190.07	$190.05	$190.10
Purchase #2	$35.88	11.577%	$40.0338	$40.03	$40.05	$40.00
Purchase #3	$130.85	9.417%	$143.1721	$143.17	$143.15	$143.20
Purchase #4	$230.52	5.756%	$243.7887	$243.79	$243.80	$243.80
Purchase #5	$118.83	10.848%	$131.7207	$131.72	$131.70	$131.70
Purchase #6	$96.43	4.600%	$100.8658	$100.87	$100.85	$100.90
Purchase #7	$91.65	8.171%	$99.1387	$99.14	$99.15	$99.10
7 purchase totals =	$872.60		$948.7892	$948.79	$948.75	$948.80