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	$131.75	10.608%	$145.726	$145.73	$145.75	$145.70
Purchase #2	$139.28	12.119%	$156.1593	$156.16	$156.15	$156.20
Purchase #3	$112.46	4.196%	$117.1788	$117.18	$117.20	$117.20
Purchase #4	$160.26	13.514%	$181.9175	$181.92	$181.90	$181.90
Purchase #5	$145.25	9.497%	$159.0444	$159.04	$159.05	$159.00
Purchase #6	$56.75	4.317%	$59.1999	$59.20	$59.20	$59.20
Purchase #7	$173.96	11.557%	$194.0646	$194.06	$194.05	$194.10
7 purchase totals =	$919.71		$1,013.2905	$1,013.29	$1,013.30	$1,013.30