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	$105.80	10.177%	$116.5673	$116.57	$116.55	$116.60
Purchase #2	$48.46	9.132%	$52.8854	$52.89	$52.90	$52.90
Purchase #3	$26.69	12.169%	$29.9379	$29.94	$29.95	$29.90
Purchase #4	$40.71	3.434%	$42.108	$42.11	$42.10	$42.10
Purchase #5	$32.25	12.109%	$36.1552	$36.16	$36.15	$36.20
Purchase #6	$12.77	4.520%	$13.3472	$13.35	$13.35	$13.30
Purchase #7	$36.99	13.653%	$42.0402	$42.04	$42.05	$42.00
7 purchase totals =	$303.67		$333.0412	$333.06	$333.05	$333.00