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	$230.27	4.298%	$240.167	$240.17	$240.15	$240.20
Purchase #2	$216.74	4.230%	$225.9081	$225.91	$225.90	$225.90
Purchase #3	$154.59	7.259%	$165.8117	$165.81	$165.80	$165.80
Purchase #4	$99.29	12.651%	$111.8512	$111.85	$111.85	$111.90
Purchase #5	$150.60	4.134%	$156.8258	$156.83	$156.85	$156.80
Purchase #6	$215.31	3.336%	$222.4927	$222.49	$222.50	$222.50
Purchase #7	$66.35	10.855%	$73.5523	$73.55	$73.55	$73.60
7 purchase totals =	$1,133.15		$1,196.6088	$1,196.61	$1,196.60	$1,196.70