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	$172.54	7.594%	$185.6427	$185.64	$185.65	$185.60
Purchase #2	$191.79	12.286%	$215.3533	$215.35	$215.35	$215.40
Purchase #3	$133.89	12.463%	$150.5767	$150.58	$150.60	$150.60
Purchase #4	$98.42	5.836%	$104.1638	$104.16	$104.15	$104.20
Purchase #5	$35.86	7.522%	$38.5574	$38.56	$38.55	$38.60
Purchase #6	$140.72	9.301%	$153.8084	$153.81	$153.80	$153.80
Purchase #7	$170.46	11.761%	$190.5078	$190.51	$190.50	$190.50
7 purchase totals =	$943.68		$1,038.6101	$1,038.61	$1,038.60	$1,038.70