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	$164.44	12.440%	$184.8963	$184.90	$184.90	$184.90
Purchase #2	$126.62	6.553%	$134.9174	$134.92	$134.90	$134.90
Purchase #3	$54.42	12.588%	$61.2704	$61.27	$61.25	$61.30
Purchase #4	$49.53	10.702%	$54.8307	$54.83	$54.85	$54.80
Purchase #5	$231.64	13.838%	$263.6943	$263.69	$263.70	$263.70
Purchase #6	$142.88	10.510%	$157.8967	$157.90	$157.90	$157.90
Purchase #7	$150.52	4.283%	$156.9668	$156.97	$156.95	$157.00
7 purchase totals =	$920.05		$1,014.4726	$1,014.48	$1,014.45	$1,014.50