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	$99.73	3.360%	$103.0809	$103.08	$103.10	$103.10
Purchase #2	$154.96	6.158%	$164.5024	$164.50	$164.50	$164.50
Purchase #3	$93.52	3.856%	$97.1261	$97.13	$97.15	$97.10
Purchase #4	$222.91	9.656%	$244.4342	$244.43	$244.45	$244.40
Purchase #5	$90.25	5.540%	$95.2499	$95.25	$95.25	$95.20
Purchase #6	$37.51	13.334%	$42.5116	$42.51	$42.50	$42.50
Purchase #7	$94.28	3.533%	$97.6109	$97.61	$97.60	$97.60
7 purchase totals =	$793.16		$844.5160	$844.51	$844.55	$844.40