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	$108.59	9.462%	$118.8648	$118.86	$118.85	$118.90
Purchase #2	$90.98	8.826%	$99.0099	$99.01	$99.00	$99.00
Purchase #3	$155.33	4.219%	$161.8834	$161.88	$161.90	$161.90
Purchase #4	$156.29	11.810%	$174.7478	$174.75	$174.75	$174.70
Purchase #5	$184.73	5.321%	$194.5595	$194.56	$194.55	$194.60
Purchase #6	$217.41	10.549%	$240.3446	$240.34	$240.35	$240.30
Purchase #7	$237.52	4.627%	$248.5101	$248.51	$248.50	$248.50
7 purchase totals =	$1,150.85		$1,237.9201	$1,237.91	$1,237.90	$1,237.90