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	$14.40	6.528%	$15.34	$15.34	$15.35	$15.30
Purchase #2	$98.55	3.626%	$102.1234	$102.12	$102.10	$102.10
Purchase #3	$20.51	3.834%	$21.2964	$21.30	$21.30	$21.30
Purchase #4	$61.84	5.349%	$65.1478	$65.15	$65.15	$65.10
Purchase #5	$11.63	11.439%	$12.9604	$12.96	$12.95	$13.00
Purchase #6	$133.77	8.624%	$145.3063	$145.31	$145.30	$145.30
Purchase #7	$234.69	8.775%	$255.284	$255.28	$255.30	$255.30
7 purchase totals =	$575.39		$617.4583	$617.46	$617.45	$617.40