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	$75.61	13.458%	$85.7856	$85.79	$85.80	$85.80
Purchase #2	$212.90	6.842%	$227.4666	$227.47	$227.45	$227.50
Purchase #3	$6.49	11.180%	$7.2156	$7.22	$7.20	$7.20
Purchase #4	$96.51	9.205%	$105.3937	$105.39	$105.40	$105.40
Purchase #5	$174.85	3.622%	$181.1831	$181.18	$181.20	$181.20
Purchase #6	$152.25	11.278%	$169.4208	$169.42	$169.40	$169.40
Purchase #7	$10.86	9.316%	$11.8717	$11.87	$11.85	$11.90
7 purchase totals =	$729.47		$788.3371	$788.34	$788.30	$788.40