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	$231.43	5.302%	$243.7004	$243.70	$243.70	$243.70
Purchase #2	$85.57	4.168%	$89.1366	$89.14	$89.15	$89.10
Purchase #3	$10.81	13.619%	$12.2822	$12.28	$12.30	$12.30
Purchase #4	$36.42	7.298%	$39.0779	$39.08	$39.10	$39.10
Purchase #5	$243.33	5.586%	$256.9224	$256.92	$256.90	$256.90
Purchase #6	$34.80	10.361%	$38.4056	$38.41	$38.40	$38.40
Purchase #7	$244.28	3.584%	$253.035	$253.04	$253.05	$253.00
7 purchase totals =	$886.64		$932.5601	$932.57	$932.60	$932.50