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	$165.55	13.726%	$188.2734	$188.27	$188.25	$188.30
Purchase #2	$54.27	12.515%	$61.0619	$61.06	$61.05	$61.10
Purchase #3	$207.77	6.582%	$221.4454	$221.45	$221.45	$221.40
Purchase #4	$23.37	10.800%	$25.894	$25.89	$25.90	$25.90
Purchase #5	$34.82	6.719%	$37.1596	$37.16	$37.15	$37.20
Purchase #6	$110.55	4.824%	$115.8829	$115.88	$115.90	$115.90
Purchase #7	$47.94	13.844%	$54.5768	$54.58	$54.60	$54.60
7 purchase totals =	$644.27		$704.2940	$704.29	$704.30	$704.40