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	$64.36	11.380%	$71.6842	$71.68	$71.70	$71.70
Purchase #2	$100.95	13.495%	$114.5732	$114.57	$114.55	$114.60
Purchase #3	$43.98	9.395%	$48.1119	$48.11	$48.10	$48.10
Purchase #4	$102.63	10.671%	$113.5816	$113.58	$113.60	$113.60
Purchase #5	$67.87	5.517%	$71.6144	$71.61	$71.60	$71.60
Purchase #6	$232.47	3.768%	$241.2295	$241.23	$241.25	$241.20
Purchase #7	$49.47	4.295%	$51.5947	$51.59	$51.60	$51.60
7 purchase totals =	$661.73		$712.3895	$712.37	$712.40	$712.40