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	$139.25	4.578%	$145.6249	$145.62	$145.60	$145.60
Purchase #2	$163.87	13.260%	$185.5992	$185.60	$185.60	$185.60
Purchase #3	$51.74	9.786%	$56.8033	$56.80	$56.80	$56.80
Purchase #4	$35.34	8.690%	$38.411	$38.41	$38.40	$38.40
Purchase #5	$227.91	12.216%	$255.7515	$255.75	$255.75	$255.80
Purchase #6	$6.83	8.124%	$7.3849	$7.38	$7.40	$7.40
Purchase #7	$54.71	3.464%	$56.6052	$56.61	$56.60	$56.60
7 purchase totals =	$679.65		$746.1800	$746.17	$746.15	$746.20