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	$155.63	11.504%	$173.5337	$173.53	$173.55	$173.50
Purchase #2	$46.45	5.633%	$49.0665	$49.07	$49.05	$49.10
Purchase #3	$220.49	11.265%	$245.3282	$245.33	$245.35	$245.30
Purchase #4	$175.41	12.261%	$196.917	$196.92	$196.90	$196.90
Purchase #5	$45.77	5.221%	$48.1597	$48.16	$48.15	$48.20
Purchase #6	$213.58	12.498%	$240.2732	$240.27	$240.25	$240.30
Purchase #7	$89.90	10.273%	$99.1354	$99.14	$99.15	$99.10
7 purchase totals =	$947.23		$1,052.4137	$1,052.42	$1,052.40	$1,052.40