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	$155.61	8.436%	$168.7373	$168.74	$168.75	$168.70
Purchase #2	$5.43	8.504%	$5.8918	$5.89	$5.90	$5.90
Purchase #3	$174.67	10.567%	$193.1274	$193.13	$193.15	$193.10
Purchase #4	$119.98	6.303%	$127.5423	$127.54	$127.55	$127.50
Purchase #5	$157.69	13.338%	$178.7227	$178.72	$178.70	$178.70
Purchase #6	$100.74	10.349%	$111.1656	$111.17	$111.15	$111.20
Purchase #7	$177.66	8.405%	$192.5923	$192.59	$192.60	$192.60
7 purchase totals =	$891.78		$977.7794	$977.78	$977.80	$977.70