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	$118.42	10.432%	$130.7736	$130.77	$130.75	$130.80
Purchase #2	$186.28	7.699%	$200.6217	$200.62	$200.60	$200.60
Purchase #3	$56.69	10.599%	$62.6986	$62.70	$62.70	$62.70
Purchase #4	$86.93	4.151%	$90.5385	$90.54	$90.55	$90.50
Purchase #5	$227.86	6.228%	$242.0511	$242.05	$242.05	$242.10
Purchase #6	$199.66	11.520%	$222.6608	$222.66	$222.65	$222.70
Purchase #7	$53.67	6.222%	$57.0093	$57.01	$57.00	$57.00
7 purchase totals =	$929.51		$1,006.3536	$1,006.35	$1,006.30	$1,006.40