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	$230.57	8.142%	$249.343	$249.34	$249.35	$249.30
Purchase #2	$149.41	8.165%	$161.6093	$161.61	$161.60	$161.60
Purchase #3	$37.55	3.583%	$38.8954	$38.90	$38.90	$38.90
Purchase #4	$61.31	10.630%	$67.8273	$67.83	$67.85	$67.80
Purchase #5	$65.71	9.709%	$72.0898	$72.09	$72.10	$72.10
Purchase #6	$198.49	12.662%	$223.6228	$223.62	$223.60	$223.60
Purchase #7	$247.92	4.333%	$258.6624	$258.66	$258.65	$258.70
7 purchase totals =	$990.96		$1,072.0500	$1,072.05	$1,072.05	$1,072.00