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	$248.84	9.141%	$271.5865	$271.59	$271.60	$271.60
Purchase #2	$227.67	8.414%	$246.8262	$246.83	$246.85	$246.80
Purchase #3	$87.75	8.426%	$95.1438	$95.14	$95.15	$95.10
Purchase #4	$103.79	5.301%	$109.2919	$109.29	$109.30	$109.30
Purchase #5	$182.38	7.775%	$196.56	$196.56	$196.55	$196.60
Purchase #6	$153.69	8.540%	$166.8151	$166.82	$166.80	$166.80
Purchase #7	$148.76	8.680%	$161.6724	$161.67	$161.65	$161.70
7 purchase totals =	$1,152.88		$1,247.8959	$1,247.90	$1,247.90	$1,247.90