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	$59.71	10.236%	$65.8219	$65.82	$65.80	$65.80
Purchase #2	$66.67	7.846%	$71.9009	$71.90	$71.90	$71.90
Purchase #3	$93.42	3.317%	$96.5187	$96.52	$96.50	$96.50
Purchase #4	$34.43	12.323%	$38.6728	$38.67	$38.65	$38.70
Purchase #5	$104.46	11.528%	$116.5021	$116.50	$116.50	$116.50
Purchase #6	$21.27	6.241%	$22.5975	$22.60	$22.60	$22.60
Purchase #7	$246.69	13.367%	$279.6651	$279.67	$279.65	$279.70
7 purchase totals =	$626.65		$691.6790	$691.68	$691.60	$691.70