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	$98.50	13.618%	$111.9137	$111.91	$111.90	$111.90
Purchase #2	$111.51	4.284%	$116.2871	$116.29	$116.30	$116.30
Purchase #3	$91.46	7.287%	$98.1247	$98.12	$98.10	$98.10
Purchase #4	$10.92	11.837%	$12.2126	$12.21	$12.20	$12.20
Purchase #5	$215.76	8.411%	$233.9076	$233.91	$233.90	$233.90
Purchase #6	$44.91	9.551%	$49.1994	$49.20	$49.20	$49.20
Purchase #7	$142.70	5.640%	$150.7483	$150.75	$150.75	$150.70
7 purchase totals =	$715.76		$772.3934	$772.39	$772.35	$772.30