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	$158.79	3.388%	$164.1698	$164.17	$164.15	$164.20
Purchase #2	$185.95	13.869%	$211.7394	$211.74	$211.75	$211.70
Purchase #3	$175.34	3.257%	$181.0508	$181.05	$181.05	$181.10
Purchase #4	$247.59	3.179%	$255.4609	$255.46	$255.45	$255.50
Purchase #5	$17.70	13.522%	$20.0934	$20.09	$20.10	$20.10
Purchase #6	$141.39	5.332%	$148.9289	$148.93	$148.95	$148.90
Purchase #7	$88.67	10.713%	$98.1692	$98.17	$98.15	$98.20
7 purchase totals =	$1,015.43		$1,079.6124	$1,079.61	$1,079.60	$1,079.70