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	$139.46	7.807%	$150.3476	$150.35	$150.35	$150.30
Purchase #2	$139.93	13.383%	$158.6568	$158.66	$158.65	$158.70
Purchase #3	$198.84	6.651%	$212.0648	$212.06	$212.05	$212.10
Purchase #4	$49.81	13.419%	$56.494	$56.49	$56.50	$56.50
Purchase #5	$171.67	11.393%	$191.2284	$191.23	$191.25	$191.20
Purchase #6	$183.58	9.104%	$200.2931	$200.29	$200.30	$200.30
Purchase #7	$162.33	13.113%	$183.6163	$183.62	$183.60	$183.60
7 purchase totals =	$1,045.62		$1,152.7010	$1,152.70	$1,152.70	$1,152.70