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	$172.32	11.377%	$191.9248	$191.92	$191.90	$191.90
Purchase #2	$203.94	7.543%	$219.3232	$219.32	$219.30	$219.30
Purchase #3	$209.64	5.384%	$220.927	$220.93	$220.95	$220.90
Purchase #4	$145.43	5.147%	$152.9153	$152.92	$152.90	$152.90
Purchase #5	$233.55	9.231%	$255.109	$255.11	$255.10	$255.10
Purchase #6	$77.34	9.761%	$84.8892	$84.89	$84.90	$84.90
Purchase #7	$95.49	10.748%	$105.7533	$105.75	$105.75	$105.80
7 purchase totals =	$1,137.71		$1,230.8418	$1,230.84	$1,230.80	$1,230.80