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	$140.75	4.307%	$146.8121	$146.81	$146.80	$146.80
Purchase #2	$96.33	5.732%	$101.8516	$101.85	$101.85	$101.90
Purchase #3	$73.71	9.803%	$80.9358	$80.94	$80.95	$80.90
Purchase #4	$37.99	13.412%	$43.0852	$43.09	$43.10	$43.10
Purchase #5	$138.89	10.222%	$153.0873	$153.09	$153.10	$153.10
Purchase #6	$162.88	13.867%	$185.4666	$185.47	$185.45	$185.50
Purchase #7	$110.35	7.867%	$119.0312	$119.03	$119.05	$119.00
7 purchase totals =	$760.90		$830.2698	$830.28	$830.30	$830.30