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	$55.63	12.578%	$62.6271	$62.63	$62.65	$62.60
Purchase #2	$76.91	7.398%	$82.5998	$82.60	$82.60	$82.60
Purchase #3	$236.78	5.270%	$249.2583	$249.26	$249.25	$249.30
Purchase #4	$13.50	11.330%	$15.0296	$15.03	$15.05	$15.00
Purchase #5	$132.72	4.765%	$139.0441	$139.04	$139.05	$139.00
Purchase #6	$34.53	10.484%	$38.1501	$38.15	$38.15	$38.20
Purchase #7	$114.89	11.801%	$128.4482	$128.45	$128.45	$128.40
7 purchase totals =	$664.96		$715.1572	$715.16	$715.20	$715.10