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	$191.60	8.729%	$208.3248	$208.32	$208.30	$208.30
Purchase #2	$236.81	11.433%	$263.8845	$263.88	$263.90	$263.90
Purchase #3	$100.82	6.110%	$106.9801	$106.98	$107.00	$107.00
Purchase #4	$222.57	9.870%	$244.5377	$244.54	$244.55	$244.50
Purchase #5	$99.93	3.332%	$103.2597	$103.26	$103.25	$103.30
Purchase #6	$239.37	13.262%	$271.1152	$271.12	$271.10	$271.10
Purchase #7	$101.88	9.812%	$111.8765	$111.88	$111.90	$111.90
7 purchase totals =	$1,192.98		$1,309.9785	$1,309.98	$1,310.00	$1,310.00