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	$153.61	8.467%	$166.6162	$166.62	$166.60	$166.60
Purchase #2	$32.47	3.303%	$33.5425	$33.54	$33.55	$33.50
Purchase #3	$50.60	3.253%	$52.246	$52.25	$52.25	$52.20
Purchase #4	$67.46	7.403%	$72.4541	$72.45	$72.45	$72.50
Purchase #5	$189.28	8.291%	$204.9732	$204.97	$204.95	$205.00
Purchase #6	$87.98	8.303%	$95.285	$95.29	$95.30	$95.30
Purchase #7	$85.58	10.450%	$94.5231	$94.52	$94.50	$94.50
7 purchase totals =	$666.98		$719.6401	$719.64	$719.60	$719.60