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	$116.30	12.552%	$130.898	$130.90	$130.90	$130.90
Purchase #2	$130.65	9.306%	$142.8083	$142.81	$142.80	$142.80
Purchase #3	$170.70	8.520%	$185.2436	$185.24	$185.25	$185.20
Purchase #4	$62.97	11.290%	$70.0793	$70.08	$70.10	$70.10
Purchase #5	$132.78	8.698%	$144.3292	$144.33	$144.35	$144.30
Purchase #6	$85.60	6.194%	$90.9021	$90.90	$90.90	$90.90
Purchase #7	$203.54	13.226%	$230.4602	$230.46	$230.45	$230.50
7 purchase totals =	$902.54		$994.7207	$994.72	$994.75	$994.70