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	$223.42	3.681%	$231.6441	$231.64	$231.65	$231.60
Purchase #2	$82.42	9.507%	$90.2557	$90.26	$90.25	$90.30
Purchase #3	$5.84	5.136%	$6.1399	$6.14	$6.15	$6.10
Purchase #4	$224.25	10.790%	$248.4466	$248.45	$248.45	$248.40
Purchase #5	$61.48	8.758%	$66.8644	$66.86	$66.85	$66.90
Purchase #6	$153.82	8.209%	$166.4471	$166.45	$166.45	$166.40
Purchase #7	$89.44	7.244%	$95.919	$95.92	$95.90	$95.90
7 purchase totals =	$840.67		$905.7168	$905.72	$905.70	$905.60