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	$175.57	9.751%	$192.6898	$192.69	$192.70	$192.70
Purchase #2	$71.56	13.854%	$81.4739	$81.47	$81.45	$81.50
Purchase #3	$93.55	7.669%	$100.7243	$100.72	$100.70	$100.70
Purchase #4	$41.38	9.824%	$45.4452	$45.45	$45.45	$45.40
Purchase #5	$126.97	10.457%	$140.2473	$140.25	$140.25	$140.20
Purchase #6	$230.52	6.336%	$245.1257	$245.13	$245.15	$245.10
Purchase #7	$126.83	4.198%	$132.1543	$132.15	$132.15	$132.20
7 purchase totals =	$866.38		$937.8605	$937.86	$937.85	$937.80