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	$66.84	4.449%	$69.8137	$69.81	$69.80	$69.80
Purchase #2	$189.80	3.534%	$196.5075	$196.51	$196.50	$196.50
Purchase #3	$101.95	12.863%	$115.0638	$115.06	$115.05	$115.10
Purchase #4	$62.58	3.233%	$64.6032	$64.60	$64.60	$64.60
Purchase #5	$127.63	11.314%	$142.0701	$142.07	$142.05	$142.10
Purchase #6	$133.68	13.788%	$152.1118	$152.11	$152.10	$152.10
Purchase #7	$104.83	6.249%	$111.3808	$111.38	$111.40	$111.40
7 purchase totals =	$787.31		$851.5509	$851.54	$851.50	$851.60