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	$52.55	4.520%	$54.9253	$54.93	$54.95	$54.90
Purchase #2	$165.77	3.751%	$171.988	$171.99	$172.00	$172.00
Purchase #3	$190.66	7.808%	$205.5467	$205.55	$205.55	$205.50
Purchase #4	$151.32	10.316%	$166.9302	$166.93	$166.95	$166.90
Purchase #5	$95.57	7.810%	$103.034	$103.03	$103.05	$103.00
Purchase #6	$151.75	5.469%	$160.0492	$160.05	$160.05	$160.00
Purchase #7	$145.51	9.509%	$159.3465	$159.35	$159.35	$159.30
7 purchase totals =	$953.13		$1,021.8199	$1,021.83	$1,021.90	$1,021.60