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	$65.82	11.200%	$73.1918	$73.19	$73.20	$73.20
Purchase #2	$47.87	5.471%	$50.489	$50.49	$50.50	$50.50
Purchase #3	$36.89	3.533%	$38.1933	$38.19	$38.20	$38.20
Purchase #4	$146.79	3.105%	$151.3478	$151.35	$151.35	$151.30
Purchase #5	$169.89	6.404%	$180.7698	$180.77	$180.75	$180.80
Purchase #6	$86.67	4.572%	$90.6326	$90.63	$90.65	$90.60
Purchase #7	$19.88	12.261%	$22.3175	$22.32	$22.30	$22.30
7 purchase totals =	$573.81		$606.9418	$606.94	$606.95	$606.90