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	$46.56	4.439%	$48.6268	$48.63	$48.65	$48.60
Purchase #2	$92.70	12.679%	$104.4534	$104.45	$104.45	$104.50
Purchase #3	$223.42	12.221%	$250.7242	$250.72	$250.70	$250.70
Purchase #4	$198.45	4.419%	$207.2195	$207.22	$207.20	$207.20
Purchase #5	$142.76	13.405%	$161.897	$161.90	$161.90	$161.90
Purchase #6	$110.93	5.683%	$117.2342	$117.23	$117.25	$117.20
Purchase #7	$70.50	10.773%	$78.095	$78.10	$78.10	$78.10
7 purchase totals =	$885.32		$968.2501	$968.25	$968.25	$968.20