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	$166.34	4.440%	$173.7255	$173.73	$173.75	$173.70
Purchase #2	$130.53	11.336%	$145.3269	$145.33	$145.35	$145.30
Purchase #3	$189.49	5.769%	$200.4217	$200.42	$200.40	$200.40
Purchase #4	$72.67	8.129%	$78.5773	$78.58	$78.60	$78.60
Purchase #5	$201.43	11.601%	$224.7979	$224.80	$224.80	$224.80
Purchase #6	$81.72	9.649%	$89.6052	$89.61	$89.60	$89.60
Purchase #7	$176.38	13.211%	$199.6816	$199.68	$199.70	$199.70
7 purchase totals =	$1,018.56		$1,112.1361	$1,112.15	$1,112.20	$1,112.10