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	$203.52	11.593%	$227.1141	$227.11	$227.10	$227.10
Purchase #2	$191.40	12.665%	$215.6408	$215.64	$215.65	$215.60
Purchase #3	$17.64	5.198%	$18.5569	$18.56	$18.55	$18.60
Purchase #4	$55.74	12.154%	$62.5146	$62.51	$62.50	$62.50
Purchase #5	$248.97	9.615%	$272.9085	$272.91	$272.90	$272.90
Purchase #6	$222.86	6.228%	$236.7397	$236.74	$236.75	$236.70
Purchase #7	$134.59	3.398%	$139.1634	$139.16	$139.15	$139.20
7 purchase totals =	$1,074.72		$1,172.6380	$1,172.63	$1,172.60	$1,172.60