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	$99.75	6.730%	$106.4632	$106.46	$106.45	$106.50
Purchase #2	$86.54	5.862%	$91.613	$91.61	$91.60	$91.60
Purchase #3	$236.85	12.723%	$266.9844	$266.98	$267.00	$267.00
Purchase #4	$69.96	11.752%	$78.1817	$78.18	$78.20	$78.20
Purchase #5	$63.56	6.361%	$67.6031	$67.60	$67.60	$67.60
Purchase #6	$8.27	3.845%	$8.588	$8.59	$8.60	$8.60
Purchase #7	$41.93	6.806%	$44.7838	$44.78	$44.80	$44.80
7 purchase totals =	$606.86		$664.2172	$664.20	$664.25	$664.30