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	$69.37	9.559%	$76.0011	$76.00	$76.00	$76.00
Purchase #2	$151.94	11.570%	$169.5195	$169.52	$169.50	$169.50
Purchase #3	$116.83	12.538%	$131.4781	$131.48	$131.50	$131.50
Purchase #4	$237.50	10.721%	$262.9624	$262.96	$262.95	$263.00
Purchase #5	$214.64	9.250%	$234.4942	$234.49	$234.50	$234.50
Purchase #6	$68.91	3.144%	$71.0765	$71.08	$71.10	$71.10
Purchase #7	$246.98	3.250%	$255.0069	$255.01	$255.00	$255.00
7 purchase totals =	$1,106.17		$1,200.5387	$1,200.54	$1,200.55	$1,200.60