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	$170.61	3.239%	$176.1361	$176.14	$176.15	$176.10
Purchase #2	$247.39	10.758%	$274.0042	$274.00	$274.00	$274.00
Purchase #3	$71.83	6.758%	$76.6843	$76.68	$76.70	$76.70
Purchase #4	$102.68	12.105%	$115.1094	$115.11	$115.10	$115.10
Purchase #5	$108.59	13.483%	$123.2312	$123.23	$123.25	$123.20
Purchase #6	$129.33	10.488%	$142.8941	$142.89	$142.90	$142.90
Purchase #7	$111.54	6.149%	$118.3986	$118.40	$118.40	$118.40
7 purchase totals =	$941.97		$1,026.4579	$1,026.45	$1,026.50	$1,026.40