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	$143.32	5.240%	$150.83	$150.83	$150.85	$150.80
Purchase #2	$11.97	6.351%	$12.7302	$12.73	$12.75	$12.70
Purchase #3	$41.84	12.401%	$47.0286	$47.03	$47.05	$47.00
Purchase #4	$76.35	12.861%	$86.1694	$86.17	$86.15	$86.20
Purchase #5	$78.70	4.448%	$82.2006	$82.20	$82.20	$82.20
Purchase #6	$79.41	13.813%	$90.3789	$90.38	$90.40	$90.40
Purchase #7	$140.70	8.459%	$152.6018	$152.60	$152.60	$152.60
7 purchase totals =	$572.29		$621.9395	$621.94	$622.00	$621.90