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	$238.45	5.535%	$251.6482	$251.65	$251.65	$251.60
Purchase #2	$79.82	12.422%	$89.7352	$89.74	$89.75	$89.70
Purchase #3	$98.50	4.490%	$102.9227	$102.92	$102.90	$102.90
Purchase #4	$163.67	13.340%	$185.5036	$185.50	$185.50	$185.50
Purchase #5	$38.60	4.755%	$40.4354	$40.44	$40.45	$40.40
Purchase #6	$211.64	6.163%	$224.6834	$224.68	$224.70	$224.70
Purchase #7	$109.75	8.299%	$118.8582	$118.86	$118.85	$118.90
7 purchase totals =	$940.43		$1,013.7867	$1,013.79	$1,013.80	$1,013.70