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	$246.72	7.659%	$265.6163	$265.62	$265.60	$265.60
Purchase #2	$205.63	5.162%	$216.2446	$216.24	$216.25	$216.20
Purchase #3	$82.72	12.125%	$92.7498	$92.75	$92.75	$92.70
Purchase #4	$161.63	13.729%	$183.8202	$183.82	$183.80	$183.80
Purchase #5	$107.83	6.172%	$114.4853	$114.49	$114.50	$114.50
Purchase #6	$147.34	3.523%	$152.5308	$152.53	$152.55	$152.50
Purchase #7	$200.31	11.149%	$222.6426	$222.64	$222.65	$222.60
7 purchase totals =	$1,152.18		$1,248.0896	$1,248.09	$1,248.10	$1,247.90