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	$95.65	6.476%	$101.8443	$101.84	$101.85	$101.80
Purchase #2	$139.47	5.859%	$147.6415	$147.64	$147.65	$147.60
Purchase #3	$99.40	4.763%	$104.1344	$104.13	$104.15	$104.10
Purchase #4	$153.45	8.547%	$166.5654	$166.57	$166.55	$166.60
Purchase #5	$147.37	5.683%	$155.745	$155.75	$155.75	$155.70
Purchase #6	$207.66	7.334%	$222.8898	$222.89	$222.90	$222.90
Purchase #7	$174.71	8.832%	$190.1404	$190.14	$190.15	$190.10
7 purchase totals =	$1,017.71		$1,088.9608	$1,088.96	$1,089.00	$1,088.80