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	$30.31	8.130%	$32.7742	$32.77	$32.75	$32.80
Purchase #2	$230.76	13.226%	$261.2803	$261.28	$261.30	$261.30
Purchase #3	$40.41	13.267%	$45.7712	$45.77	$45.75	$45.80
Purchase #4	$237.59	6.323%	$252.6128	$252.61	$252.60	$252.60
Purchase #5	$80.95	6.127%	$85.9098	$85.91	$85.90	$85.90
Purchase #6	$174.72	5.847%	$184.9359	$184.94	$184.95	$184.90
Purchase #7	$20.31	4.669%	$21.2583	$21.26	$21.25	$21.30
7 purchase totals =	$815.05		$884.5425	$884.54	$884.50	$884.60