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	$79.37	8.443%	$86.0712	$86.07	$86.05	$86.10
Purchase #2	$105.91	13.681%	$120.3995	$120.40	$120.40	$120.40
Purchase #3	$85.50	5.371%	$90.0922	$90.09	$90.10	$90.10
Purchase #4	$5.98	7.677%	$6.4391	$6.44	$6.45	$6.40
Purchase #5	$73.82	6.707%	$78.7711	$78.77	$78.75	$78.80
Purchase #6	$144.75	12.407%	$162.7091	$162.71	$162.70	$162.70
Purchase #7	$167.84	3.647%	$173.9611	$173.96	$173.95	$174.00
7 purchase totals =	$663.17		$718.4433	$718.44	$718.40	$718.50