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	$102.51	8.597%	$111.3228	$111.32	$111.30	$111.30
Purchase #2	$151.57	4.579%	$158.5104	$158.51	$158.50	$158.50
Purchase #3	$221.44	13.447%	$251.217	$251.22	$251.20	$251.20
Purchase #4	$113.27	3.627%	$117.3783	$117.38	$117.40	$117.40
Purchase #5	$69.29	4.586%	$72.4676	$72.47	$72.45	$72.50
Purchase #6	$64.73	9.389%	$70.8075	$70.81	$70.80	$70.80
Purchase #7	$199.54	8.277%	$216.0559	$216.06	$216.05	$216.10
7 purchase totals =	$922.35		$997.7595	$997.77	$997.70	$997.80