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	$71.40	5.514%	$75.337	$75.34	$75.35	$75.30
Purchase #2	$19.69	10.104%	$21.6795	$21.68	$21.70	$21.70
Purchase #3	$178.95	6.661%	$190.8699	$190.87	$190.85	$190.90
Purchase #4	$43.67	13.252%	$49.4571	$49.46	$49.45	$49.50
Purchase #5	$48.73	12.362%	$54.754	$54.75	$54.75	$54.80
Purchase #6	$197.45	5.604%	$208.5151	$208.52	$208.50	$208.50
Purchase #7	$100.48	5.405%	$105.9109	$105.91	$105.90	$105.90
7 purchase totals =	$660.37		$706.5235	$706.53	$706.50	$706.60