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	$165.91	5.514%	$175.0583	$175.06	$175.05	$175.10
Purchase #2	$135.94	6.162%	$144.3166	$144.32	$144.30	$144.30
Purchase #3	$5.73	6.862%	$6.1232	$6.12	$6.10	$6.10
Purchase #4	$240.26	5.614%	$253.7482	$253.75	$253.75	$253.70
Purchase #5	$171.28	11.303%	$190.6398	$190.64	$190.65	$190.60
Purchase #6	$112.44	13.871%	$128.0366	$128.04	$128.05	$128.00
Purchase #7	$105.58	12.365%	$118.635	$118.64	$118.65	$118.60
7 purchase totals =	$937.14		$1,016.5577	$1,016.57	$1,016.55	$1,016.40