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	$147.80	7.207%	$158.4519	$158.45	$158.45	$158.50
Purchase #2	$132.48	7.862%	$142.8956	$142.90	$142.90	$142.90
Purchase #3	$222.77	11.610%	$248.6336	$248.63	$248.65	$248.60
Purchase #4	$239.37	7.840%	$258.1366	$258.14	$258.15	$258.10
Purchase #5	$137.45	5.767%	$145.3767	$145.38	$145.40	$145.40
Purchase #6	$48.98	12.603%	$55.1529	$55.15	$55.15	$55.20
Purchase #7	$72.27	8.308%	$78.2742	$78.27	$78.25	$78.30
7 purchase totals =	$1,001.12		$1,086.9215	$1,086.92	$1,086.95	$1,087.00