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	$183.88	6.732%	$196.2588	$196.26	$196.25	$196.30
Purchase #2	$86.77	13.526%	$98.5065	$98.51	$98.50	$98.50
Purchase #3	$73.36	9.794%	$80.5449	$80.54	$80.55	$80.50
Purchase #4	$140.58	7.601%	$151.2655	$151.27	$151.25	$151.30
Purchase #5	$107.25	5.677%	$113.3386	$113.34	$113.35	$113.30
Purchase #6	$210.95	4.766%	$221.0039	$221.00	$221.00	$221.00
Purchase #7	$191.57	10.635%	$211.9435	$211.94	$211.95	$211.90
7 purchase totals =	$994.36		$1,072.8617	$1,072.86	$1,072.85	$1,072.80