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	$199.44	5.215%	$209.8408	$209.84	$209.85	$209.80
Purchase #2	$214.83	3.700%	$222.7787	$222.78	$222.80	$222.80
Purchase #3	$108.47	3.167%	$111.9052	$111.91	$111.90	$111.90
Purchase #4	$182.59	10.784%	$202.2805	$202.28	$202.30	$202.30
Purchase #5	$186.47	7.408%	$200.2837	$200.28	$200.30	$200.30
Purchase #6	$165.89	11.246%	$184.546	$184.55	$184.55	$184.50
Purchase #7	$70.92	9.855%	$77.9092	$77.91	$77.90	$77.90
7 purchase totals =	$1,128.61		$1,209.5441	$1,209.55	$1,209.60	$1,209.50