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	$70.56	11.705%	$78.819	$78.82	$78.80	$78.80
Purchase #2	$159.31	8.557%	$172.9422	$172.94	$172.95	$172.90
Purchase #3	$95.76	3.328%	$98.9469	$98.95	$98.95	$98.90
Purchase #4	$149.88	5.135%	$157.5763	$157.58	$157.60	$157.60
Purchase #5	$226.76	13.509%	$257.393	$257.39	$257.40	$257.40
Purchase #6	$68.90	3.783%	$71.5065	$71.51	$71.50	$71.50
Purchase #7	$188.36	5.452%	$198.6294	$198.63	$198.65	$198.60
7 purchase totals =	$959.53		$1,035.8133	$1,035.82	$1,035.85	$1,035.70