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	$165.88	13.255%	$187.8674	$187.87	$187.85	$187.90
Purchase #2	$125.46	7.568%	$134.9548	$134.95	$134.95	$135.00
Purchase #3	$225.65	13.769%	$256.7197	$256.72	$256.70	$256.70
Purchase #4	$66.80	8.455%	$72.4479	$72.45	$72.45	$72.40
Purchase #5	$56.54	4.705%	$59.2002	$59.20	$59.20	$59.20
Purchase #6	$17.82	7.363%	$19.1321	$19.13	$19.15	$19.10
Purchase #7	$75.87	8.846%	$82.5815	$82.58	$82.60	$82.60
7 purchase totals =	$734.02		$812.9036	$812.90	$812.90	$812.90