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	$104.77	11.482%	$116.7997	$116.80	$116.80	$116.80
Purchase #2	$127.75	12.416%	$143.6114	$143.61	$143.60	$143.60
Purchase #3	$222.68	5.266%	$234.4063	$234.41	$234.40	$234.40
Purchase #4	$7.39	3.126%	$7.621	$7.62	$7.60	$7.60
Purchase #5	$112.32	4.513%	$117.389	$117.39	$117.40	$117.40
Purchase #6	$86.64	3.220%	$89.4298	$89.43	$89.45	$89.40
Purchase #7	$123.98	10.291%	$136.7388	$136.74	$136.75	$136.70
7 purchase totals =	$785.53		$845.9960	$846.00	$846.00	$845.90