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	$216.53	7.813%	$233.4475	$233.45	$233.45	$233.40
Purchase #2	$14.61	11.581%	$16.302	$16.30	$16.30	$16.30
Purchase #3	$132.46	6.261%	$140.7533	$140.75	$140.75	$140.80
Purchase #4	$229.87	12.277%	$258.0911	$258.09	$258.10	$258.10
Purchase #5	$19.29	10.514%	$21.3182	$21.32	$21.30	$21.30
Purchase #6	$38.77	9.674%	$42.5206	$42.52	$42.50	$42.50
Purchase #7	$235.88	6.149%	$250.3843	$250.38	$250.40	$250.40
7 purchase totals =	$887.41		$962.8170	$962.81	$962.80	$962.80