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	$54.80	9.675%	$60.1019	$60.10	$60.10	$60.10
Purchase #2	$125.56	4.160%	$130.7833	$130.78	$130.80	$130.80
Purchase #3	$115.37	11.129%	$128.2095	$128.21	$128.20	$128.20
Purchase #4	$81.54	9.496%	$89.283	$89.28	$89.30	$89.30
Purchase #5	$135.62	6.463%	$144.3851	$144.39	$144.40	$144.40
Purchase #6	$216.77	5.164%	$227.964	$227.96	$227.95	$228.00
Purchase #7	$100.42	11.150%	$111.6168	$111.62	$111.60	$111.60
7 purchase totals =	$830.08		$892.3436	$892.34	$892.35	$892.40