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	$155.58	10.596%	$172.0653	$172.07	$172.05	$172.10
Purchase #2	$213.87	9.552%	$234.2989	$234.30	$234.30	$234.30
Purchase #3	$209.59	6.784%	$223.8086	$223.81	$223.80	$223.80
Purchase #4	$142.57	13.503%	$161.8212	$161.82	$161.80	$161.80
Purchase #5	$131.81	12.603%	$148.422	$148.42	$148.40	$148.40
Purchase #6	$147.56	6.256%	$156.7914	$156.79	$156.80	$156.80
Purchase #7	$184.87	13.752%	$210.2933	$210.29	$210.30	$210.30
7 purchase totals =	$1,185.85		$1,307.5007	$1,307.50	$1,307.45	$1,307.50