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	$115.29	6.218%	$122.4587	$122.46	$122.45	$122.50
Purchase #2	$68.65	5.532%	$72.4477	$72.45	$72.45	$72.40
Purchase #3	$95.64	9.289%	$104.524	$104.52	$104.50	$104.50
Purchase #4	$139.55	13.607%	$158.5386	$158.54	$158.55	$158.50
Purchase #5	$5.56	5.613%	$5.8721	$5.87	$5.85	$5.90
Purchase #6	$50.74	10.139%	$55.8845	$55.88	$55.90	$55.90
Purchase #7	$156.63	7.156%	$167.8384	$167.84	$167.85	$167.80
7 purchase totals =	$632.06		$687.5640	$687.56	$687.55	$687.50