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	$237.35	7.813%	$255.8942	$255.89	$255.90	$255.90
Purchase #2	$130.78	10.109%	$144.0006	$144.00	$144.00	$144.00
Purchase #3	$209.80	11.656%	$234.2543	$234.25	$234.25	$234.30
Purchase #4	$18.67	4.707%	$19.5488	$19.55	$19.55	$19.50
Purchase #5	$70.41	11.658%	$78.6184	$78.62	$78.60	$78.60
Purchase #6	$134.78	6.360%	$143.352	$143.35	$143.35	$143.40
Purchase #7	$136.28	9.306%	$148.9622	$148.96	$148.95	$149.00
7 purchase totals =	$938.07		$1,024.6305	$1,024.62	$1,024.60	$1,024.70