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	$93.66	11.587%	$104.5124	$104.51	$104.50	$104.50
Purchase #2	$140.40	8.423%	$152.2259	$152.23	$152.25	$152.20
Purchase #3	$157.68	9.685%	$172.9513	$172.95	$172.95	$173.00
Purchase #4	$221.75	4.792%	$232.3763	$232.38	$232.40	$232.40
Purchase #5	$178.29	9.852%	$195.8551	$195.86	$195.85	$195.90
Purchase #6	$160.75	7.611%	$172.9847	$172.98	$173.00	$173.00
Purchase #7	$51.71	7.411%	$55.5422	$55.54	$55.55	$55.50
7 purchase totals =	$1,004.24		$1,086.4479	$1,086.45	$1,086.50	$1,086.50