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	$38.69	5.244%	$40.7189	$40.72	$40.70	$40.70
Purchase #2	$189.63	8.349%	$205.4622	$205.46	$205.45	$205.50
Purchase #3	$34.84	4.643%	$36.4576	$36.46	$36.45	$36.50
Purchase #4	$60.79	9.714%	$66.6951	$66.70	$66.70	$66.70
Purchase #5	$79.58	3.686%	$82.5133	$82.51	$82.50	$82.50
Purchase #6	$139.49	3.562%	$144.4586	$144.46	$144.45	$144.50
Purchase #7	$152.30	8.334%	$164.9927	$164.99	$165.00	$165.00
7 purchase totals =	$695.32		$741.2984	$741.30	$741.25	$741.40