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	$116.51	9.138%	$127.1567	$127.16	$127.15	$127.20
Purchase #2	$26.26	13.594%	$29.8298	$29.83	$29.85	$29.80
Purchase #3	$100.30	13.750%	$114.0913	$114.09	$114.10	$114.10
Purchase #4	$98.44	9.714%	$108.0025	$108.00	$108.00	$108.00
Purchase #5	$116.43	9.505%	$127.4967	$127.50	$127.50	$127.50
Purchase #6	$153.64	3.841%	$159.5413	$159.54	$159.55	$159.50
Purchase #7	$228.40	12.468%	$256.8769	$256.88	$256.90	$256.90
7 purchase totals =	$839.98		$922.9952	$923.00	$923.05	$923.00