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	$158.93	8.763%	$172.857	$172.86	$172.85	$172.90
Purchase #2	$45.53	12.754%	$51.3369	$51.34	$51.35	$51.30
Purchase #3	$79.84	10.511%	$88.232	$88.23	$88.25	$88.20
Purchase #4	$71.97	7.378%	$77.2799	$77.28	$77.30	$77.30
Purchase #5	$90.75	13.859%	$103.327	$103.33	$103.35	$103.30
Purchase #6	$174.66	5.575%	$184.3973	$184.40	$184.40	$184.40
Purchase #7	$128.46	12.712%	$144.7898	$144.79	$144.80	$144.80
7 purchase totals =	$750.14		$822.2199	$822.23	$822.30	$822.20