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	$116.68	12.777%	$131.5882	$131.59	$131.60	$131.60
Purchase #2	$17.26	8.275%	$18.6883	$18.69	$18.70	$18.70
Purchase #3	$142.32	4.551%	$148.797	$148.80	$148.80	$148.80
Purchase #4	$121.69	7.170%	$130.4152	$130.42	$130.40	$130.40
Purchase #5	$137.98	4.848%	$144.6693	$144.67	$144.65	$144.70
Purchase #6	$73.39	6.647%	$78.2682	$78.27	$78.25	$78.30
Purchase #7	$98.72	11.123%	$109.7006	$109.70	$109.70	$109.70
7 purchase totals =	$708.04		$762.1268	$762.14	$762.10	$762.20