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	$32.64	4.289%	$34.0399	$34.04	$34.05	$34.00
Purchase #2	$27.72	7.820%	$29.8877	$29.89	$29.90	$29.90
Purchase #3	$145.39	4.249%	$151.5676	$151.57	$151.55	$151.60
Purchase #4	$58.82	4.500%	$61.4669	$61.47	$61.45	$61.50
Purchase #5	$13.35	4.331%	$13.9282	$13.93	$13.95	$13.90
Purchase #6	$84.86	13.108%	$95.9834	$95.98	$96.00	$96.00
Purchase #7	$161.95	11.129%	$179.9734	$179.97	$179.95	$180.00
7 purchase totals =	$524.73		$566.8471	$566.85	$566.85	$566.90