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	$231.29	8.141%	$250.1193	$250.12	$250.10	$250.10
Purchase #2	$168.95	9.499%	$184.9986	$185.00	$185.00	$185.00
Purchase #3	$200.25	13.735%	$227.7543	$227.75	$227.75	$227.80
Purchase #4	$51.43	3.249%	$53.101	$53.10	$53.10	$53.10
Purchase #5	$173.38	13.547%	$196.8678	$196.87	$196.85	$196.90
Purchase #6	$205.66	13.524%	$233.4735	$233.47	$233.45	$233.50
Purchase #7	$140.57	3.663%	$145.7191	$145.72	$145.70	$145.70
7 purchase totals =	$1,171.53		$1,292.0336	$1,292.03	$1,291.95	$1,292.10