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	$230.52	10.191%	$254.0123	$254.01	$254.00	$254.00
Purchase #2	$98.76	4.714%	$103.4155	$103.42	$103.40	$103.40
Purchase #3	$93.52	5.773%	$98.9189	$98.92	$98.90	$98.90
Purchase #4	$55.85	8.659%	$60.6861	$60.69	$60.70	$60.70
Purchase #5	$169.74	6.781%	$181.2501	$181.25	$181.25	$181.30
Purchase #6	$69.78	9.787%	$76.6094	$76.61	$76.60	$76.60
Purchase #7	$57.46	3.737%	$59.6073	$59.61	$59.60	$59.60
7 purchase totals =	$775.63		$834.4996	$834.51	$834.45	$834.50