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	$216.60	8.428%	$234.855	$234.86	$234.85	$234.90
Purchase #2	$201.63	7.408%	$216.5668	$216.57	$216.55	$216.60
Purchase #3	$40.28	13.169%	$45.5845	$45.58	$45.60	$45.60
Purchase #4	$122.37	5.821%	$129.4932	$129.49	$129.50	$129.50
Purchase #5	$107.65	10.366%	$118.809	$118.81	$118.80	$118.80
Purchase #6	$100.81	4.655%	$105.5027	$105.50	$105.50	$105.50
Purchase #7	$226.39	10.260%	$249.6176	$249.62	$249.60	$249.60
7 purchase totals =	$1,015.73		$1,100.4288	$1,100.43	$1,100.40	$1,100.50