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	$217.94	6.833%	$232.8318	$232.83	$232.85	$232.80
Purchase #2	$70.95	3.735%	$73.6	$73.60	$73.60	$73.60
Purchase #3	$21.52	3.703%	$22.3169	$22.32	$22.30	$22.30
Purchase #4	$179.46	8.141%	$194.0698	$194.07	$194.05	$194.10
Purchase #5	$92.79	8.721%	$100.8822	$100.88	$100.90	$100.90
Purchase #6	$90.33	12.127%	$101.2843	$101.28	$101.30	$101.30
Purchase #7	$42.90	12.435%	$48.2346	$48.23	$48.25	$48.20
7 purchase totals =	$715.89		$773.2196	$773.21	$773.25	$773.20