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	$192.36	11.767%	$214.995	$215.00	$215.00	$215.00
Purchase #2	$116.79	11.849%	$130.6284	$130.63	$130.65	$130.60
Purchase #3	$130.81	4.261%	$136.3838	$136.38	$136.40	$136.40
Purchase #4	$244.62	10.486%	$270.2709	$270.27	$270.25	$270.30
Purchase #5	$49.54	3.246%	$51.1481	$51.15	$51.15	$51.10
Purchase #6	$199.49	12.232%	$223.8916	$223.89	$223.90	$223.90
Purchase #7	$165.79	4.308%	$172.9322	$172.93	$172.95	$172.90
7 purchase totals =	$1,099.40		$1,200.2500	$1,200.25	$1,200.30	$1,200.20