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	$144.84	12.288%	$162.6379	$162.64	$162.65	$162.60
Purchase #2	$158.51	8.808%	$172.4716	$172.47	$172.45	$172.50
Purchase #3	$42.58	11.800%	$47.6044	$47.60	$47.60	$47.60
Purchase #4	$113.31	7.240%	$121.5136	$121.51	$121.50	$121.50
Purchase #5	$144.56	8.508%	$156.8592	$156.86	$156.85	$156.90
Purchase #6	$16.62	4.689%	$17.3993	$17.40	$17.40	$17.40
Purchase #7	$78.58	13.131%	$88.8983	$88.90	$88.90	$88.90
7 purchase totals =	$699.00		$767.3843	$767.38	$767.35	$767.40