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	$108.95	6.625%	$116.1679	$116.17	$116.15	$116.20
Purchase #2	$60.36	7.143%	$64.6715	$64.67	$64.65	$64.70
Purchase #3	$100.73	8.229%	$109.0191	$109.02	$109.00	$109.00
Purchase #4	$170.88	10.757%	$189.2616	$189.26	$189.25	$189.30
Purchase #5	$103.51	4.699%	$108.3739	$108.37	$108.35	$108.40
Purchase #6	$233.88	3.868%	$242.9265	$242.93	$242.95	$242.90
Purchase #7	$240.87	4.377%	$251.4129	$251.41	$251.40	$251.40
7 purchase totals =	$1,019.18		$1,081.8334	$1,081.83	$1,081.75	$1,081.90