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	$141.66	8.710%	$153.9986	$154.00	$154.00	$154.00
Purchase #2	$180.37	11.311%	$200.7717	$200.77	$200.75	$200.80
Purchase #3	$56.58	4.540%	$59.1487	$59.15	$59.15	$59.10
Purchase #4	$201.35	12.495%	$226.5087	$226.51	$226.50	$226.50
Purchase #5	$81.85	13.208%	$92.6607	$92.66	$92.65	$92.70
Purchase #6	$134.63	13.168%	$152.3581	$152.36	$152.35	$152.40
Purchase #7	$155.67	6.170%	$165.2748	$165.27	$165.25	$165.30
7 purchase totals =	$952.11		$1,050.7213	$1,050.72	$1,050.65	$1,050.80