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	$156.46	11.580%	$174.5781	$174.58	$174.60	$174.60
Purchase #2	$179.93	4.510%	$188.0448	$188.04	$188.05	$188.00
Purchase #3	$88.83	12.324%	$99.7774	$99.78	$99.80	$99.80
Purchase #4	$197.65	5.818%	$209.1493	$209.15	$209.15	$209.10
Purchase #5	$66.50	13.578%	$75.5294	$75.53	$75.55	$75.50
Purchase #6	$62.86	12.342%	$70.6182	$70.62	$70.60	$70.60
Purchase #7	$178.95	12.184%	$200.7533	$200.75	$200.75	$200.80
7 purchase totals =	$931.18		$1,018.4505	$1,018.45	$1,018.50	$1,018.40