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	$204.94	5.650%	$216.5191	$216.52	$216.50	$216.50
Purchase #2	$86.72	4.816%	$90.8964	$90.90	$90.90	$90.90
Purchase #3	$23.48	3.240%	$24.2408	$24.24	$24.25	$24.20
Purchase #4	$11.77	7.819%	$12.6903	$12.69	$12.70	$12.70
Purchase #5	$131.86	5.540%	$139.165	$139.17	$139.15	$139.20
Purchase #6	$11.60	6.191%	$12.3182	$12.32	$12.30	$12.30
Purchase #7	$214.48	12.186%	$240.6165	$240.62	$240.60	$240.60
7 purchase totals =	$684.85		$736.4463	$736.46	$736.40	$736.40