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	$57.32	8.616%	$62.2587	$62.26	$62.25	$62.30
Purchase #2	$152.56	6.248%	$162.0919	$162.09	$162.10	$162.10
Purchase #3	$177.77	10.495%	$196.427	$196.43	$196.45	$196.40
Purchase #4	$162.82	9.514%	$178.3107	$178.31	$178.30	$178.30
Purchase #5	$247.34	3.557%	$256.1379	$256.14	$256.15	$256.10
Purchase #6	$78.77	12.792%	$88.8463	$88.85	$88.85	$88.80
Purchase #7	$168.71	9.615%	$184.9315	$184.93	$184.95	$184.90
7 purchase totals =	$1,045.29		$1,129.0040	$1,129.01	$1,129.05	$1,128.90