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	$162.52	13.778%	$184.912	$184.91	$184.90	$184.90
Purchase #2	$232.30	10.345%	$256.3314	$256.33	$256.35	$256.30
Purchase #3	$149.64	12.338%	$168.1026	$168.10	$168.10	$168.10
Purchase #4	$80.83	10.777%	$89.541	$89.54	$89.55	$89.50
Purchase #5	$178.94	12.810%	$201.8622	$201.86	$201.85	$201.90
Purchase #6	$25.68	7.248%	$27.5413	$27.54	$27.55	$27.50
Purchase #7	$139.54	5.852%	$147.7059	$147.71	$147.70	$147.70
7 purchase totals =	$969.45		$1,075.9964	$1,075.99	$1,076.00	$1,075.90