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	$168.52	7.751%	$181.582	$181.58	$181.60	$181.60
Purchase #2	$48.55	12.803%	$54.7659	$54.77	$54.75	$54.80
Purchase #3	$78.28	12.255%	$87.8732	$87.87	$87.85	$87.90
Purchase #4	$198.63	11.601%	$221.6731	$221.67	$221.65	$221.70
Purchase #5	$149.61	3.139%	$154.3063	$154.31	$154.30	$154.30
Purchase #6	$40.34	11.195%	$44.8561	$44.86	$44.85	$44.90
Purchase #7	$76.70	10.836%	$85.0112	$85.01	$85.00	$85.00
7 purchase totals =	$760.63		$830.0678	$830.07	$830.00	$830.20