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	$122.49	11.552%	$136.64	$136.64	$136.65	$136.60
Purchase #2	$9.54	6.352%	$10.146	$10.15	$10.15	$10.10
Purchase #3	$134.40	10.193%	$148.0994	$148.10	$148.10	$148.10
Purchase #4	$170.30	8.841%	$185.3562	$185.36	$185.35	$185.40
Purchase #5	$62.62	6.223%	$66.5168	$66.52	$66.50	$66.50
Purchase #6	$45.92	7.762%	$49.4843	$49.48	$49.50	$49.50
Purchase #7	$89.55	11.542%	$99.8859	$99.89	$99.90	$99.90
7 purchase totals =	$634.82		$696.1286	$696.14	$696.15	$696.10