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	$23.28	10.711%	$25.7735	$25.77	$25.75	$25.80
Purchase #2	$210.49	11.859%	$235.452	$235.45	$235.45	$235.50
Purchase #3	$130.25	8.375%	$141.1584	$141.16	$141.15	$141.20
Purchase #4	$214.45	5.512%	$226.2705	$226.27	$226.25	$226.30
Purchase #5	$211.86	5.193%	$222.8619	$222.86	$222.85	$222.90
Purchase #6	$134.64	6.676%	$143.6286	$143.63	$143.65	$143.60
Purchase #7	$95.95	10.119%	$105.6592	$105.66	$105.65	$105.70
7 purchase totals =	$1,020.92		$1,100.8041	$1,100.80	$1,100.75	$1,101.00