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	$96.77	3.228%	$99.8937	$99.89	$99.90	$99.90
Purchase #2	$21.94	3.789%	$22.7713	$22.77	$22.75	$22.80
Purchase #3	$232.30	13.329%	$263.2633	$263.26	$263.25	$263.30
Purchase #4	$98.54	7.580%	$106.0093	$106.01	$106.00	$106.00
Purchase #5	$37.39	7.328%	$40.1299	$40.13	$40.15	$40.10
Purchase #6	$115.52	10.606%	$127.7721	$127.77	$127.75	$127.80
Purchase #7	$89.64	5.105%	$94.2161	$94.22	$94.20	$94.20
7 purchase totals =	$692.10		$754.0557	$754.05	$754.00	$754.10