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	$213.28	6.699%	$227.5676	$227.57	$227.55	$227.60
Purchase #2	$24.52	13.192%	$27.7547	$27.75	$27.75	$27.80
Purchase #3	$97.38	11.146%	$108.234	$108.23	$108.25	$108.20
Purchase #4	$233.57	8.558%	$253.5589	$253.56	$253.55	$253.60
Purchase #5	$75.71	4.192%	$78.8838	$78.88	$78.90	$78.90
Purchase #6	$198.95	11.815%	$222.4559	$222.46	$222.45	$222.50
Purchase #7	$74.34	9.711%	$81.5592	$81.56	$81.55	$81.60
7 purchase totals =	$917.75		$1,000.0141	$1,000.01	$1,000.00	$1,000.20