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	$146.83	13.545%	$166.7181	$166.72	$166.70	$166.70
Purchase #2	$173.62	9.809%	$190.6504	$190.65	$190.65	$190.70
Purchase #3	$145.86	9.741%	$160.0682	$160.07	$160.05	$160.10
Purchase #4	$215.41	10.533%	$238.0991	$238.10	$238.10	$238.10
Purchase #5	$135.83	10.521%	$150.1207	$150.12	$150.10	$150.10
Purchase #6	$32.87	12.642%	$37.0254	$37.03	$37.05	$37.00
Purchase #7	$202.49	5.839%	$214.3134	$214.31	$214.30	$214.30
7 purchase totals =	$1,052.91		$1,156.9953	$1,157.00	$1,156.95	$1,157.00