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	$89.34	5.594%	$94.3377	$94.34	$94.35	$94.30
Purchase #2	$55.92	6.797%	$59.7209	$59.72	$59.70	$59.70
Purchase #3	$26.41	3.286%	$27.2778	$27.28	$27.30	$27.30
Purchase #4	$77.89	5.599%	$82.2511	$82.25	$82.25	$82.30
Purchase #5	$144.80	10.366%	$159.81	$159.81	$159.80	$159.80
Purchase #6	$136.37	7.445%	$146.5227	$146.52	$146.50	$146.50
Purchase #7	$212.53	10.223%	$234.2569	$234.26	$234.25	$234.30
7 purchase totals =	$743.26		$804.1771	$804.18	$804.15	$804.20