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	$131.38	9.738%	$144.1738	$144.17	$144.15	$144.20
Purchase #2	$202.35	7.760%	$218.0524	$218.05	$218.05	$218.10
Purchase #3	$75.91	3.274%	$78.3953	$78.40	$78.40	$78.40
Purchase #4	$166.57	8.158%	$180.1588	$180.16	$180.15	$180.20
Purchase #5	$108.92	3.117%	$112.315	$112.32	$112.30	$112.30
Purchase #6	$49.69	9.871%	$54.5949	$54.59	$54.60	$54.60
Purchase #7	$161.52	7.486%	$173.6114	$173.61	$173.60	$173.60
7 purchase totals =	$896.34		$961.3016	$961.30	$961.25	$961.40