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	$202.73	8.468%	$219.8972	$219.90	$219.90	$219.90
Purchase #2	$79.85	13.741%	$90.8222	$90.82	$90.80	$90.80
Purchase #3	$127.72	5.310%	$134.5019	$134.50	$134.50	$134.50
Purchase #4	$95.51	12.378%	$107.3322	$107.33	$107.35	$107.30
Purchase #5	$102.50	8.516%	$111.2289	$111.23	$111.25	$111.20
Purchase #6	$202.54	9.810%	$222.4092	$222.41	$222.40	$222.40
Purchase #7	$143.45	6.105%	$152.2076	$152.21	$152.20	$152.20
7 purchase totals =	$954.30		$1,038.3992	$1,038.40	$1,038.40	$1,038.30