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	$196.87	6.551%	$209.767	$209.77	$209.75	$209.80
Purchase #2	$127.50	8.358%	$138.1565	$138.16	$138.15	$138.20
Purchase #3	$163.26	9.360%	$178.5411	$178.54	$178.55	$178.50
Purchase #4	$77.45	6.291%	$82.3224	$82.32	$82.30	$82.30
Purchase #5	$65.38	3.417%	$67.614	$67.61	$67.60	$67.60
Purchase #6	$82.68	11.193%	$91.9344	$91.93	$91.95	$91.90
Purchase #7	$161.28	12.547%	$181.5158	$181.52	$181.50	$181.50
7 purchase totals =	$874.42		$949.8512	$949.85	$949.80	$949.80