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	$166.75	9.477%	$182.5529	$182.55	$182.55	$182.60
Purchase #2	$244.50	9.175%	$266.9329	$266.93	$266.95	$266.90
Purchase #3	$183.33	9.342%	$200.4567	$200.46	$200.45	$200.50
Purchase #4	$21.98	11.180%	$24.4374	$24.44	$24.45	$24.40
Purchase #5	$95.89	3.769%	$99.5041	$99.50	$99.50	$99.50
Purchase #6	$43.72	3.402%	$45.2074	$45.21	$45.20	$45.20
Purchase #7	$240.65	6.741%	$256.8722	$256.87	$256.85	$256.90
7 purchase totals =	$996.82		$1,075.9636	$1,075.96	$1,075.95	$1,076.00