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	$158.66	13.768%	$180.5043	$180.50	$180.50	$180.50
Purchase #2	$173.81	13.142%	$196.6521	$196.65	$196.65	$196.70
Purchase #3	$17.96	13.848%	$20.4471	$20.45	$20.45	$20.40
Purchase #4	$155.92	8.755%	$169.5708	$169.57	$169.55	$169.60
Purchase #5	$199.82	12.655%	$225.1072	$225.11	$225.10	$225.10
Purchase #6	$86.31	5.763%	$91.284	$91.28	$91.30	$91.30
Purchase #7	$211.53	4.341%	$220.7125	$220.71	$220.70	$220.70
7 purchase totals =	$1,004.01		$1,104.2780	$1,104.27	$1,104.25	$1,104.30