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	$64.53	4.731%	$67.5829	$67.58	$67.60	$67.60
Purchase #2	$88.79	12.380%	$99.7822	$99.78	$99.80	$99.80
Purchase #3	$107.47	10.386%	$118.6318	$118.63	$118.65	$118.60
Purchase #4	$113.38	13.355%	$128.5219	$128.52	$128.50	$128.50
Purchase #5	$58.36	5.642%	$61.6527	$61.65	$61.65	$61.70
Purchase #6	$36.87	5.799%	$39.0081	$39.01	$39.00	$39.00
Purchase #7	$182.37	10.146%	$200.8733	$200.87	$200.85	$200.90
7 purchase totals =	$651.77		$716.0529	$716.04	$716.05	$716.10