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	$145.86	13.211%	$165.1296	$165.13	$165.15	$165.10
Purchase #2	$184.38	5.686%	$194.8638	$194.86	$194.85	$194.90
Purchase #3	$124.68	9.499%	$136.5234	$136.52	$136.50	$136.50
Purchase #4	$82.27	8.432%	$89.207	$89.21	$89.20	$89.20
Purchase #5	$63.78	5.117%	$67.0436	$67.04	$67.05	$67.00
Purchase #6	$142.32	7.830%	$153.4637	$153.46	$153.45	$153.50
Purchase #7	$53.32	7.828%	$57.4939	$57.49	$57.50	$57.50
7 purchase totals =	$796.61		$863.7250	$863.71	$863.70	$863.70