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	$145.38	4.385%	$151.7549	$151.75	$151.75	$151.80
Purchase #2	$152.89	5.182%	$160.8128	$160.81	$160.80	$160.80
Purchase #3	$34.64	13.431%	$39.2925	$39.29	$39.30	$39.30
Purchase #4	$151.61	13.418%	$171.953	$171.95	$171.95	$172.00
Purchase #5	$104.26	11.370%	$116.1144	$116.11	$116.10	$116.10
Purchase #6	$52.90	9.296%	$57.8176	$57.82	$57.80	$57.80
Purchase #7	$12.75	4.282%	$13.296	$13.30	$13.30	$13.30
7 purchase totals =	$654.43		$711.0412	$711.03	$711.00	$711.10