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	$219.93	13.803%	$250.2869	$250.29	$250.30	$250.30
Purchase #2	$209.30	3.689%	$217.0211	$217.02	$217.00	$217.00
Purchase #3	$150.42	4.292%	$156.876	$156.88	$156.90	$156.90
Purchase #4	$70.58	10.747%	$78.1652	$78.17	$78.15	$78.20
Purchase #5	$95.60	8.638%	$103.8579	$103.86	$103.85	$103.90
Purchase #6	$219.28	11.268%	$243.9885	$243.99	$244.00	$244.00
Purchase #7	$24.96	3.678%	$25.878	$25.88	$25.90	$25.90
7 purchase totals =	$990.07		$1,076.0736	$1,076.09	$1,076.10	$1,076.20