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	$103.89	5.732%	$109.845	$109.85	$109.85	$109.80
Purchase #2	$246.41	11.351%	$274.38	$274.38	$274.40	$274.40
Purchase #3	$163.83	5.105%	$172.1935	$172.19	$172.20	$172.20
Purchase #4	$181.92	10.274%	$200.6105	$200.61	$200.60	$200.60
Purchase #5	$133.97	4.542%	$140.0549	$140.05	$140.05	$140.10
Purchase #6	$152.29	6.626%	$162.3807	$162.38	$162.40	$162.40
Purchase #7	$236.41	13.625%	$268.6209	$268.62	$268.60	$268.60
7 purchase totals =	$1,218.72		$1,328.0855	$1,328.08	$1,328.10	$1,328.10