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	$75.80	9.299%	$82.8486	$82.85	$82.85	$82.80
Purchase #2	$57.80	10.333%	$63.7725	$63.77	$63.75	$63.80
Purchase #3	$152.44	6.530%	$162.3943	$162.39	$162.40	$162.40
Purchase #4	$176.84	10.846%	$196.0201	$196.02	$196.00	$196.00
Purchase #5	$44.49	10.644%	$49.2255	$49.23	$49.25	$49.20
Purchase #6	$137.67	6.153%	$146.1408	$146.14	$146.15	$146.10
Purchase #7	$162.52	13.839%	$185.0111	$185.01	$185.00	$185.00
7 purchase totals =	$807.56		$885.4129	$885.41	$885.40	$885.30