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	$169.62	12.151%	$190.2305	$190.23	$190.25	$190.20
Purchase #2	$226.54	10.447%	$250.2066	$250.21	$250.20	$250.20
Purchase #3	$107.50	5.782%	$113.7157	$113.72	$113.70	$113.70
Purchase #4	$46.89	12.518%	$52.7597	$52.76	$52.75	$52.80
Purchase #5	$61.46	6.318%	$65.343	$65.34	$65.35	$65.30
Purchase #6	$41.58	9.294%	$45.4444	$45.44	$45.45	$45.40
Purchase #7	$34.45	11.308%	$38.3456	$38.35	$38.35	$38.30
7 purchase totals =	$688.04		$756.0455	$756.05	$756.05	$755.90