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	$156.56	7.499%	$168.3004	$168.30	$168.30	$168.30
Purchase #2	$17.96	12.128%	$20.1382	$20.14	$20.15	$20.10
Purchase #3	$69.55	13.146%	$78.693	$78.69	$78.70	$78.70
Purchase #4	$214.94	7.193%	$230.4006	$230.40	$230.40	$230.40
Purchase #5	$152.85	7.808%	$164.7845	$164.78	$164.80	$164.80
Purchase #6	$239.89	13.696%	$272.7453	$272.75	$272.75	$272.70
Purchase #7	$63.27	4.238%	$65.9514	$65.95	$65.95	$66.00
7 purchase totals =	$915.02		$1,001.0134	$1,001.01	$1,001.05	$1,001.00