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	$210.46	3.233%	$217.2642	$217.26	$217.25	$217.30
Purchase #2	$81.77	13.601%	$92.8915	$92.89	$92.90	$92.90
Purchase #3	$231.26	12.795%	$260.8497	$260.85	$260.85	$260.80
Purchase #4	$86.47	10.392%	$95.456	$95.46	$95.45	$95.50
Purchase #5	$247.58	8.755%	$269.2556	$269.26	$269.25	$269.30
Purchase #6	$64.65	12.122%	$72.4869	$72.49	$72.50	$72.50
Purchase #7	$74.27	11.329%	$82.684	$82.68	$82.70	$82.70
7 purchase totals =	$996.46		$1,090.8879	$1,090.89	$1,090.90	$1,091.00