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	$34.73	8.380%	$37.6404	$37.64	$37.65	$37.60
Purchase #2	$53.51	3.363%	$55.3095	$55.31	$55.30	$55.30
Purchase #3	$58.63	13.220%	$66.3809	$66.38	$66.40	$66.40
Purchase #4	$194.69	5.574%	$205.542	$205.54	$205.55	$205.50
Purchase #5	$28.46	6.354%	$30.2683	$30.27	$30.25	$30.30
Purchase #6	$231.80	3.851%	$240.7266	$240.73	$240.75	$240.70
Purchase #7	$127.61	9.389%	$139.5913	$139.59	$139.60	$139.60
7 purchase totals =	$729.43		$775.4590	$775.46	$775.50	$775.40