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	$83.42	3.652%	$86.4665	$86.47	$86.45	$86.50
Purchase #2	$51.53	4.136%	$53.6613	$53.66	$53.65	$53.70
Purchase #3	$26.64	6.127%	$28.2722	$28.27	$28.25	$28.30
Purchase #4	$74.25	12.393%	$83.4518	$83.45	$83.45	$83.50
Purchase #5	$174.54	7.674%	$187.9342	$187.93	$187.95	$187.90
Purchase #6	$107.66	3.350%	$111.2666	$111.27	$111.25	$111.30
Purchase #7	$175.57	8.316%	$190.1704	$190.17	$190.15	$190.20
7 purchase totals =	$693.61		$741.2230	$741.22	$741.15	$741.40