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	$41.64	9.179%	$45.4621	$45.46	$45.45	$45.50
Purchase #2	$70.52	13.651%	$80.1467	$80.15	$80.15	$80.10
Purchase #3	$145.81	10.819%	$161.5852	$161.59	$161.60	$161.60
Purchase #4	$197.72	6.123%	$209.8264	$209.83	$209.85	$209.80
Purchase #5	$32.72	5.652%	$34.5693	$34.57	$34.55	$34.60
Purchase #6	$97.46	8.283%	$105.5326	$105.53	$105.55	$105.50
Purchase #7	$95.43	3.844%	$99.0983	$99.10	$99.10	$99.10
7 purchase totals =	$681.30		$736.2206	$736.23	$736.25	$736.20