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	$65.62	13.466%	$74.4564	$74.46	$74.45	$74.50
Purchase #2	$236.78	9.191%	$258.5424	$258.54	$258.55	$258.50
Purchase #3	$238.58	6.347%	$253.7227	$253.72	$253.70	$253.70
Purchase #4	$109.75	12.857%	$123.8606	$123.86	$123.85	$123.90
Purchase #5	$64.31	10.200%	$70.8696	$70.87	$70.85	$70.90
Purchase #6	$72.91	8.171%	$78.8675	$78.87	$78.85	$78.90
Purchase #7	$156.77	12.409%	$176.2236	$176.22	$176.20	$176.20
7 purchase totals =	$944.72		$1,036.5428	$1,036.54	$1,036.45	$1,036.60