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	$77.58	7.194%	$83.1611	$83.16	$83.15	$83.20
Purchase #2	$80.35	13.149%	$90.9152	$90.92	$90.90	$90.90
Purchase #3	$242.55	6.387%	$258.0417	$258.04	$258.05	$258.00
Purchase #4	$32.59	4.740%	$34.1348	$34.13	$34.15	$34.10
Purchase #5	$232.37	13.124%	$262.8662	$262.87	$262.85	$262.90
Purchase #6	$153.27	7.233%	$164.356	$164.36	$164.35	$164.40
Purchase #7	$114.99	9.265%	$125.6438	$125.64	$125.65	$125.60
7 purchase totals =	$933.70		$1,019.1188	$1,019.12	$1,019.10	$1,019.10