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	$229.25	13.685%	$260.6229	$260.62	$260.60	$260.60
Purchase #2	$75.94	6.434%	$80.826	$80.83	$80.85	$80.80
Purchase #3	$145.46	12.450%	$163.5698	$163.57	$163.55	$163.60
Purchase #4	$84.95	6.701%	$90.6425	$90.64	$90.65	$90.60
Purchase #5	$198.71	8.607%	$215.813	$215.81	$215.80	$215.80
Purchase #6	$131.55	3.626%	$136.32	$136.32	$136.30	$136.30
Purchase #7	$243.73	3.857%	$253.1307	$253.13	$253.15	$253.10
7 purchase totals =	$1,109.59		$1,200.9249	$1,200.92	$1,200.90	$1,200.80