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	$14.95	6.361%	$15.901	$15.90	$15.90	$15.90
Purchase #2	$8.98	13.577%	$10.1992	$10.20	$10.20	$10.20
Purchase #3	$223.56	6.224%	$237.4744	$237.47	$237.45	$237.50
Purchase #4	$238.44	7.663%	$256.7117	$256.71	$256.70	$256.70
Purchase #5	$52.58	9.248%	$57.4426	$57.44	$57.45	$57.40
Purchase #6	$156.40	11.274%	$174.0325	$174.03	$174.05	$174.00
Purchase #7	$233.88	13.356%	$265.117	$265.12	$265.10	$265.10
7 purchase totals =	$928.79		$1,016.8784	$1,016.87	$1,016.85	$1,016.80