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	$74.62	13.292%	$84.5385	$84.54	$84.55	$84.50
Purchase #2	$103.82	10.414%	$114.6318	$114.63	$114.65	$114.60
Purchase #3	$154.90	3.677%	$160.5957	$160.60	$160.60	$160.60
Purchase #4	$212.74	7.409%	$228.5019	$228.50	$228.50	$228.50
Purchase #5	$224.59	7.518%	$241.4747	$241.47	$241.45	$241.50
Purchase #6	$29.75	8.380%	$32.2431	$32.24	$32.25	$32.20
Purchase #7	$173.47	13.309%	$196.5571	$196.56	$196.55	$196.60
7 purchase totals =	$973.89		$1,058.5428	$1,058.54	$1,058.55	$1,058.50