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	$152.45	5.404%	$160.6884	$160.69	$160.70	$160.70
Purchase #2	$213.60	4.357%	$222.9066	$222.91	$222.90	$222.90
Purchase #3	$129.54	3.811%	$134.4768	$134.48	$134.50	$134.50
Purchase #4	$14.55	5.760%	$15.3881	$15.39	$15.40	$15.40
Purchase #5	$175.77	13.501%	$199.5007	$199.50	$199.50	$199.50
Purchase #6	$119.42	9.804%	$131.1279	$131.13	$131.15	$131.10
Purchase #7	$146.48	4.813%	$153.5301	$153.53	$153.55	$153.50
7 purchase totals =	$951.81		$1,017.6186	$1,017.63	$1,017.70	$1,017.60