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	$90.75	11.436%	$101.1282	$101.13	$101.15	$101.10
Purchase #2	$46.95	11.832%	$52.5051	$52.51	$52.50	$52.50
Purchase #3	$238.66	7.636%	$256.8841	$256.88	$256.90	$256.90
Purchase #4	$220.35	11.220%	$245.0733	$245.07	$245.05	$245.10
Purchase #5	$179.74	5.748%	$190.0715	$190.07	$190.05	$190.10
Purchase #6	$180.72	13.596%	$205.2907	$205.29	$205.30	$205.30
Purchase #7	$123.89	3.777%	$128.5693	$128.57	$128.55	$128.60
7 purchase totals =	$1,081.06		$1,179.5222	$1,179.52	$1,179.50	$1,179.60