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	$99.61	5.746%	$105.3336	$105.33	$105.35	$105.30
Purchase #2	$224.81	7.745%	$242.2215	$242.22	$242.20	$242.20
Purchase #3	$236.70	9.456%	$259.0824	$259.08	$259.10	$259.10
Purchase #4	$26.83	11.830%	$30.004	$30.00	$30.00	$30.00
Purchase #5	$152.97	3.874%	$158.8961	$158.90	$158.90	$158.90
Purchase #6	$128.34	12.145%	$143.9269	$143.93	$143.95	$143.90
Purchase #7	$96.96	8.436%	$105.1395	$105.14	$105.15	$105.10
7 purchase totals =	$966.22		$1,044.6040	$1,044.60	$1,044.65	$1,044.50