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	$227.80	8.801%	$247.8487	$247.85	$247.85	$247.80
Purchase #2	$81.94	13.409%	$92.9273	$92.93	$92.95	$92.90
Purchase #3	$31.41	5.601%	$33.1693	$33.17	$33.15	$33.20
Purchase #4	$56.72	6.763%	$60.556	$60.56	$60.55	$60.60
Purchase #5	$53.29	11.491%	$59.4136	$59.41	$59.40	$59.40
Purchase #6	$118.98	9.459%	$130.2343	$130.23	$130.25	$130.20
Purchase #7	$165.85	6.141%	$176.0348	$176.03	$176.05	$176.00
7 purchase totals =	$735.99		$800.1840	$800.18	$800.20	$800.10