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	$166.27	10.702%	$184.0642	$184.06	$184.05	$184.10
Purchase #2	$175.45	3.423%	$181.4557	$181.46	$181.45	$181.50
Purchase #3	$14.42	13.665%	$16.3905	$16.39	$16.40	$16.40
Purchase #4	$181.66	5.344%	$191.3679	$191.37	$191.35	$191.40
Purchase #5	$71.51	6.817%	$76.3848	$76.38	$76.40	$76.40
Purchase #6	$19.41	4.655%	$20.3135	$20.31	$20.30	$20.30
Purchase #7	$164.37	12.806%	$185.4192	$185.42	$185.40	$185.40
7 purchase totals =	$793.09		$855.3958	$855.39	$855.35	$855.50