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	$97.44	6.395%	$103.6713	$103.67	$103.65	$103.70
Purchase #2	$224.64	7.479%	$241.4408	$241.44	$241.45	$241.40
Purchase #3	$241.56	13.774%	$274.8325	$274.83	$274.85	$274.80
Purchase #4	$27.26	4.297%	$28.4314	$28.43	$28.45	$28.40
Purchase #5	$229.78	10.391%	$253.6564	$253.66	$253.65	$253.70
Purchase #6	$90.78	10.704%	$100.4971	$100.50	$100.50	$100.50
Purchase #7	$37.43	11.823%	$41.8553	$41.86	$41.85	$41.90
7 purchase totals =	$948.89		$1,044.3848	$1,044.39	$1,044.40	$1,044.40