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	$81.60	13.726%	$92.8004	$92.80	$92.80	$92.80
Purchase #2	$104.47	6.874%	$111.6513	$111.65	$111.65	$111.70
Purchase #3	$139.73	8.739%	$151.941	$151.94	$151.95	$151.90
Purchase #4	$245.41	8.450%	$266.1471	$266.15	$266.15	$266.10
Purchase #5	$198.39	12.311%	$222.8138	$222.81	$222.80	$222.80
Purchase #6	$216.86	8.732%	$235.7962	$235.80	$235.80	$235.80
Purchase #7	$245.46	4.357%	$256.1547	$256.15	$256.15	$256.20
7 purchase totals =	$1,231.92		$1,337.3045	$1,337.30	$1,337.30	$1,337.30