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	$150.25	4.459%	$156.9496	$156.95	$156.95	$156.90
Purchase #2	$225.94	13.128%	$255.6014	$255.60	$255.60	$255.60
Purchase #3	$24.89	9.624%	$27.2854	$27.29	$27.30	$27.30
Purchase #4	$165.70	5.470%	$174.7638	$174.76	$174.75	$174.80
Purchase #5	$226.29	13.557%	$256.9681	$256.97	$256.95	$257.00
Purchase #6	$209.26	10.812%	$231.8852	$231.89	$231.90	$231.90
Purchase #7	$58.43	8.468%	$63.3779	$63.38	$63.40	$63.40
7 purchase totals =	$1,060.76		$1,166.8314	$1,166.84	$1,166.85	$1,166.90