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	$83.43	3.635%	$86.4627	$86.46	$86.45	$86.50
Purchase #2	$134.31	10.773%	$148.7792	$148.78	$148.80	$148.80
Purchase #3	$114.43	12.256%	$128.4545	$128.45	$128.45	$128.50
Purchase #4	$58.38	11.786%	$65.2607	$65.26	$65.25	$65.30
Purchase #5	$196.93	5.178%	$207.127	$207.13	$207.15	$207.10
Purchase #6	$203.69	13.240%	$230.6586	$230.66	$230.65	$230.70
Purchase #7	$124.33	10.703%	$137.637	$137.64	$137.65	$137.60
7 purchase totals =	$915.50		$1,004.3797	$1,004.38	$1,004.40	$1,004.50