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	$124.32	6.653%	$132.591	$132.59	$132.60	$132.60
Purchase #2	$10.80	8.839%	$11.7546	$11.75	$11.75	$11.80
Purchase #3	$18.90	10.421%	$20.8696	$20.87	$20.85	$20.90
Purchase #4	$144.56	11.305%	$160.9025	$160.90	$160.90	$160.90
Purchase #5	$9.64	13.267%	$10.9189	$10.92	$10.90	$10.90
Purchase #6	$198.49	13.645%	$225.574	$225.57	$225.55	$225.60
Purchase #7	$250.79	12.496%	$282.1287	$282.13	$282.15	$282.10
7 purchase totals =	$757.50		$844.7393	$844.73	$844.70	$844.80