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	$76.42	5.440%	$80.5772	$80.58	$80.60	$80.60
Purchase #2	$69.97	4.170%	$72.8877	$72.89	$72.90	$72.90
Purchase #3	$50.67	7.451%	$54.4454	$54.45	$54.45	$54.40
Purchase #4	$110.63	6.736%	$118.082	$118.08	$118.10	$118.10
Purchase #5	$82.55	6.335%	$87.7795	$87.78	$87.80	$87.80
Purchase #6	$55.75	11.291%	$62.0447	$62.04	$62.05	$62.00
Purchase #7	$95.80	3.289%	$98.9509	$98.95	$98.95	$99.00
7 purchase totals =	$541.79		$574.7674	$574.77	$574.85	$574.80