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	$189.35	10.213%	$208.6883	$208.69	$208.70	$208.70
Purchase #2	$6.61	3.218%	$6.8227	$6.82	$6.80	$6.80
Purchase #3	$100.98	10.136%	$111.2153	$111.22	$111.20	$111.20
Purchase #4	$132.86	4.301%	$138.5743	$138.57	$138.55	$138.60
Purchase #5	$119.34	10.809%	$132.2395	$132.24	$132.25	$132.20
Purchase #6	$242.77	13.342%	$275.1604	$275.16	$275.15	$275.20
Purchase #7	$156.81	8.605%	$170.3035	$170.30	$170.30	$170.30
7 purchase totals =	$948.72		$1,043.0040	$1,043.00	$1,042.95	$1,043.00