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	$239.60	7.811%	$258.3152	$258.32	$258.30	$258.30
Purchase #2	$172.99	13.514%	$196.3679	$196.37	$196.35	$196.40
Purchase #3	$217.48	11.121%	$241.666	$241.67	$241.65	$241.70
Purchase #4	$63.83	5.619%	$67.4166	$67.42	$67.40	$67.40
Purchase #5	$38.78	8.623%	$42.124	$42.12	$42.10	$42.10
Purchase #6	$226.75	7.596%	$243.9739	$243.97	$243.95	$244.00
Purchase #7	$9.58	5.827%	$10.1382	$10.14	$10.15	$10.10
7 purchase totals =	$969.01		$1,060.0018	$1,060.01	$1,059.90	$1,060.00