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	$185.95	10.171%	$204.863	$204.86	$204.85	$204.90
Purchase #2	$145.39	3.433%	$150.3812	$150.38	$150.40	$150.40
Purchase #3	$12.52	9.720%	$13.7369	$13.74	$13.75	$13.70
Purchase #4	$68.56	13.777%	$78.0055	$78.01	$78.00	$78.00
Purchase #5	$14.52	4.275%	$15.1407	$15.14	$15.15	$15.10
Purchase #6	$51.25	11.702%	$57.2473	$57.25	$57.25	$57.20
Purchase #7	$210.59	4.522%	$220.1129	$220.11	$220.10	$220.10
7 purchase totals =	$688.78		$739.4875	$739.49	$739.50	$739.40