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	$92.40	3.259%	$95.4113	$95.41	$95.40	$95.40
Purchase #2	$19.81	4.616%	$20.7244	$20.72	$20.70	$20.70
Purchase #3	$144.32	12.744%	$162.7121	$162.71	$162.70	$162.70
Purchase #4	$140.78	3.111%	$145.1597	$145.16	$145.15	$145.20
Purchase #5	$11.54	10.145%	$12.7107	$12.71	$12.70	$12.70
Purchase #6	$95.58	6.177%	$101.484	$101.48	$101.50	$101.50
Purchase #7	$211.34	10.674%	$233.8984	$233.90	$233.90	$233.90
7 purchase totals =	$715.77		$772.1006	$772.09	$772.05	$772.10