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	$129.80	10.524%	$143.4602	$143.46	$143.45	$143.50
Purchase #2	$93.96	5.405%	$99.0385	$99.04	$99.05	$99.00
Purchase #3	$166.28	3.520%	$172.1331	$172.13	$172.15	$172.10
Purchase #4	$97.35	8.524%	$105.6481	$105.65	$105.65	$105.60
Purchase #5	$31.31	10.384%	$34.5612	$34.56	$34.55	$34.60
Purchase #6	$230.33	12.809%	$259.833	$259.83	$259.85	$259.80
Purchase #7	$185.62	10.866%	$205.7895	$205.79	$205.80	$205.80
7 purchase totals =	$934.65		$1,020.4636	$1,020.46	$1,020.50	$1,020.40