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	$17.70	3.550%	$18.3284	$18.33	$18.35	$18.30
Purchase #2	$158.82	9.743%	$174.2938	$174.29	$174.30	$174.30
Purchase #3	$78.85	13.177%	$89.2401	$89.24	$89.25	$89.20
Purchase #4	$145.25	10.433%	$160.4039	$160.40	$160.40	$160.40
Purchase #5	$168.55	11.609%	$188.117	$188.12	$188.10	$188.10
Purchase #6	$205.32	12.731%	$231.4593	$231.46	$231.45	$231.50
Purchase #7	$189.78	4.489%	$198.2992	$198.30	$198.30	$198.30
7 purchase totals =	$964.27		$1,060.1417	$1,060.14	$1,060.15	$1,060.10