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	$77.47	11.855%	$86.6541	$86.65	$86.65	$86.70
Purchase #2	$38.63	7.845%	$41.6605	$41.66	$41.65	$41.70
Purchase #3	$178.94	9.136%	$195.288	$195.29	$195.30	$195.30
Purchase #4	$211.57	10.278%	$233.3152	$233.32	$233.30	$233.30
Purchase #5	$173.79	3.440%	$179.7684	$179.77	$179.75	$179.80
Purchase #6	$236.83	9.536%	$259.4141	$259.41	$259.40	$259.40
Purchase #7	$94.66	6.354%	$100.6747	$100.67	$100.65	$100.70
7 purchase totals =	$1,011.89		$1,096.7750	$1,096.77	$1,096.70	$1,096.90