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	$96.70	12.665%	$108.9471	$108.95	$108.95	$108.90
Purchase #2	$81.45	10.208%	$89.7644	$89.76	$89.75	$89.80
Purchase #3	$75.58	4.404%	$78.9085	$78.91	$78.90	$78.90
Purchase #4	$165.42	12.406%	$185.942	$185.94	$185.95	$185.90
Purchase #5	$72.62	13.543%	$82.4549	$82.45	$82.45	$82.50
Purchase #6	$187.58	12.598%	$211.2113	$211.21	$211.20	$211.20
Purchase #7	$219.60	3.122%	$226.4559	$226.46	$226.45	$226.50
7 purchase totals =	$898.95		$983.6841	$983.68	$983.65	$983.70