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	$139.66	8.301%	$151.2532	$151.25	$151.25	$151.30
Purchase #2	$125.86	4.828%	$131.9365	$131.94	$131.95	$131.90
Purchase #3	$150.36	6.366%	$159.9319	$159.93	$159.95	$159.90
Purchase #4	$173.89	10.266%	$191.7415	$191.74	$191.75	$191.70
Purchase #5	$65.82	6.704%	$70.2326	$70.23	$70.25	$70.20
Purchase #6	$177.81	11.583%	$198.4057	$198.41	$198.40	$198.40
Purchase #7	$154.31	11.436%	$171.9569	$171.96	$171.95	$172.00
7 purchase totals =	$987.71		$1,075.4583	$1,075.46	$1,075.50	$1,075.40