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	$50.90	12.476%	$57.2503	$57.25	$57.25	$57.30
Purchase #2	$87.58	13.727%	$99.6021	$99.60	$99.60	$99.60
Purchase #3	$101.71	13.531%	$115.4724	$115.47	$115.45	$115.50
Purchase #4	$159.86	7.840%	$172.393	$172.39	$172.40	$172.40
Purchase #5	$133.42	7.810%	$143.8401	$143.84	$143.85	$143.80
Purchase #6	$243.89	11.568%	$272.1032	$272.10	$272.10	$272.10
Purchase #7	$90.81	12.647%	$102.2947	$102.29	$102.30	$102.30
7 purchase totals =	$868.17		$962.9558	$962.94	$962.95	$963.00