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	$152.97	13.811%	$174.0967	$174.10	$174.10	$174.10
Purchase #2	$48.93	10.395%	$54.0163	$54.02	$54.00	$54.00
Purchase #3	$10.57	9.732%	$11.5987	$11.60	$11.60	$11.60
Purchase #4	$161.64	4.303%	$168.5954	$168.60	$168.60	$168.60
Purchase #5	$172.76	3.379%	$178.5976	$178.60	$178.60	$178.60
Purchase #6	$17.37	6.873%	$18.5638	$18.56	$18.55	$18.60
Purchase #7	$30.90	5.315%	$32.5423	$32.54	$32.55	$32.50
7 purchase totals =	$595.14		$638.0108	$638.02	$638.00	$638.00