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	$101.30	3.347%	$104.6905	$104.69	$104.70	$104.70
Purchase #2	$89.42	8.410%	$96.9402	$96.94	$96.95	$96.90
Purchase #3	$194.70	10.391%	$214.9313	$214.93	$214.95	$214.90
Purchase #4	$155.71	10.382%	$171.8758	$171.88	$171.90	$171.90
Purchase #5	$117.31	5.175%	$123.3808	$123.38	$123.40	$123.40
Purchase #6	$246.84	11.647%	$275.5895	$275.59	$275.60	$275.60
Purchase #7	$161.78	13.823%	$184.1428	$184.14	$184.15	$184.10
7 purchase totals =	$1,067.06		$1,171.5509	$1,171.55	$1,171.65	$1,171.50