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	$121.39	7.285%	$130.2333	$130.23	$130.25	$130.20
Purchase #2	$140.75	4.773%	$147.468	$147.47	$147.45	$147.50
Purchase #3	$161.51	3.458%	$167.095	$167.10	$167.10	$167.10
Purchase #4	$150.41	7.342%	$161.4531	$161.45	$161.45	$161.50
Purchase #5	$43.58	4.626%	$45.596	$45.60	$45.60	$45.60
Purchase #6	$191.88	9.536%	$210.1777	$210.18	$210.20	$210.20
Purchase #7	$100.45	3.308%	$103.7729	$103.77	$103.75	$103.80
7 purchase totals =	$909.97		$965.7960	$965.80	$965.80	$965.90