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	$158.59	4.771%	$166.1563	$166.16	$166.15	$166.20
Purchase #2	$43.78	10.418%	$48.341	$48.34	$48.35	$48.30
Purchase #3	$231.54	10.517%	$255.8911	$255.89	$255.90	$255.90
Purchase #4	$166.94	11.249%	$185.7191	$185.72	$185.70	$185.70
Purchase #5	$96.27	9.450%	$105.3675	$105.37	$105.35	$105.40
Purchase #6	$81.73	7.789%	$88.0959	$88.10	$88.10	$88.10
Purchase #7	$153.25	8.666%	$166.5306	$166.53	$166.55	$166.50
7 purchase totals =	$932.10		$1,016.1015	$1,016.11	$1,016.10	$1,016.10