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	$53.32	10.663%	$59.0055	$59.01	$59.00	$59.00
Purchase #2	$175.86	4.635%	$184.0111	$184.01	$184.00	$184.00
Purchase #3	$104.99	8.389%	$113.7976	$113.80	$113.80	$113.80
Purchase #4	$213.90	4.807%	$224.1822	$224.18	$224.20	$224.20
Purchase #5	$40.61	4.464%	$42.4228	$42.42	$42.40	$42.40
Purchase #6	$123.45	6.679%	$131.6952	$131.70	$131.70	$131.70
Purchase #7	$59.42	7.635%	$63.9567	$63.96	$63.95	$64.00
7 purchase totals =	$771.55		$819.0711	$819.08	$819.05	$819.10