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	$127.91	11.718%	$142.8985	$142.90	$142.90	$142.90
Purchase #2	$163.32	13.472%	$185.3225	$185.32	$185.30	$185.30
Purchase #3	$112.38	6.853%	$120.0814	$120.08	$120.10	$120.10
Purchase #4	$172.44	6.336%	$183.3658	$183.37	$183.35	$183.40
Purchase #5	$151.42	9.506%	$165.814	$165.81	$165.80	$165.80
Purchase #6	$63.95	8.617%	$69.4606	$69.46	$69.45	$69.50
Purchase #7	$101.25	3.861%	$105.1593	$105.16	$105.15	$105.20
7 purchase totals =	$892.67		$972.1021	$972.10	$972.05	$972.20