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	$140.88	5.152%	$148.1381	$148.14	$148.15	$148.10
Purchase #2	$39.95	7.816%	$43.0725	$43.07	$43.05	$43.10
Purchase #3	$193.64	9.841%	$212.6961	$212.70	$212.70	$212.70
Purchase #4	$224.41	6.298%	$238.5433	$238.54	$238.55	$238.50
Purchase #5	$206.70	10.267%	$227.9219	$227.92	$227.90	$227.90
Purchase #6	$180.40	3.871%	$187.3833	$187.38	$187.40	$187.40
Purchase #7	$145.65	13.351%	$165.0957	$165.10	$165.10	$165.10
7 purchase totals =	$1,131.63		$1,222.8509	$1,222.85	$1,222.85	$1,222.80