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	$180.91	8.427%	$196.1553	$196.16	$196.15	$196.20
Purchase #2	$156.34	10.499%	$172.7541	$172.75	$172.75	$172.80
Purchase #3	$157.91	4.730%	$165.3791	$165.38	$165.40	$165.40
Purchase #4	$116.62	3.497%	$120.6982	$120.70	$120.70	$120.70
Purchase #5	$51.34	6.307%	$54.578	$54.58	$54.60	$54.60
Purchase #6	$162.80	6.812%	$173.8899	$173.89	$173.90	$173.90
Purchase #7	$87.80	7.776%	$94.6273	$94.63	$94.65	$94.60
7 purchase totals =	$913.72		$978.0819	$978.09	$978.15	$978.20