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	$144.44	5.822%	$152.8493	$152.85	$152.85	$152.80
Purchase #2	$33.90	3.145%	$34.9662	$34.97	$34.95	$35.00
Purchase #3	$29.70	6.121%	$31.5179	$31.52	$31.50	$31.50
Purchase #4	$139.87	10.712%	$154.8529	$154.85	$154.85	$154.90
Purchase #5	$112.72	9.102%	$122.9798	$122.98	$123.00	$123.00
Purchase #6	$152.58	11.385%	$169.9512	$169.95	$169.95	$170.00
Purchase #7	$59.54	10.820%	$65.9822	$65.98	$66.00	$66.00
7 purchase totals =	$672.75		$733.0995	$733.10	$733.10	$733.20