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	$143.54	13.381%	$162.7471	$162.75	$162.75	$162.70
Purchase #2	$126.56	12.670%	$142.5952	$142.60	$142.60	$142.60
Purchase #3	$211.72	12.488%	$238.1596	$238.16	$238.15	$238.20
Purchase #4	$162.39	7.416%	$174.4328	$174.43	$174.45	$174.40
Purchase #5	$43.49	13.345%	$49.2937	$49.29	$49.30	$49.30
Purchase #6	$162.35	11.834%	$181.5625	$181.56	$181.55	$181.60
Purchase #7	$44.83	11.608%	$50.0339	$50.03	$50.05	$50.00
7 purchase totals =	$894.88		$998.8248	$998.82	$998.85	$998.80