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	$109.28	5.212%	$114.9757	$114.98	$115.00	$115.00
Purchase #2	$131.98	9.702%	$144.7847	$144.78	$144.80	$144.80
Purchase #3	$28.51	12.325%	$32.0239	$32.02	$32.00	$32.00
Purchase #4	$76.92	10.826%	$85.2474	$85.25	$85.25	$85.20
Purchase #5	$119.54	6.275%	$127.0411	$127.04	$127.05	$127.00
Purchase #6	$112.27	13.748%	$127.7049	$127.70	$127.70	$127.70
Purchase #7	$195.35	5.130%	$205.3715	$205.37	$205.35	$205.40
7 purchase totals =	$773.85		$837.1492	$837.14	$837.15	$837.10