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	$125.81	5.370%	$132.566	$132.57	$132.55	$132.60
Purchase #2	$113.41	4.286%	$118.2708	$118.27	$118.25	$118.30
Purchase #3	$32.47	3.282%	$33.5357	$33.54	$33.55	$33.50
Purchase #4	$236.68	3.696%	$245.4277	$245.43	$245.45	$245.40
Purchase #5	$246.82	6.504%	$262.8732	$262.87	$262.85	$262.90
Purchase #6	$74.51	10.297%	$82.1823	$82.18	$82.20	$82.20
Purchase #7	$118.61	9.729%	$130.1496	$130.15	$130.15	$130.10
7 purchase totals =	$948.31		$1,005.0053	$1,005.01	$1,005.00	$1,005.00