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	$159.33	7.705%	$171.6064	$171.61	$171.60	$171.60
Purchase #2	$98.49	13.197%	$111.4877	$111.49	$111.50	$111.50
Purchase #3	$31.25	10.419%	$34.5059	$34.51	$34.50	$34.50
Purchase #4	$17.27	3.323%	$17.8439	$17.84	$17.85	$17.80
Purchase #5	$138.35	8.492%	$150.0987	$150.10	$150.10	$150.10
Purchase #6	$211.31	8.400%	$229.06	$229.06	$229.05	$229.10
Purchase #7	$160.59	12.766%	$181.0909	$181.09	$181.10	$181.10
7 purchase totals =	$816.59		$895.6935	$895.70	$895.70	$895.70