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	$105.78	3.318%	$109.2898	$109.29	$109.30	$109.30
Purchase #2	$141.67	13.578%	$160.906	$160.91	$160.90	$160.90
Purchase #3	$164.74	5.348%	$173.5503	$173.55	$173.55	$173.60
Purchase #4	$38.91	12.645%	$43.8302	$43.83	$43.85	$43.80
Purchase #5	$99.71	5.107%	$104.8022	$104.80	$104.80	$104.80
Purchase #6	$247.92	9.776%	$272.1567	$272.16	$272.15	$272.20
Purchase #7	$136.81	8.615%	$148.5962	$148.60	$148.60	$148.60
7 purchase totals =	$935.54		$1,013.1314	$1,013.14	$1,013.15	$1,013.20