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	$119.29	3.596%	$123.5797	$123.58	$123.60	$123.60
Purchase #2	$150.31	10.611%	$166.2594	$166.26	$166.25	$166.30
Purchase #3	$198.79	11.680%	$222.0087	$222.01	$222.00	$222.00
Purchase #4	$146.89	10.278%	$161.9874	$161.99	$162.00	$162.00
Purchase #5	$199.82	6.145%	$212.0989	$212.10	$212.10	$212.10
Purchase #6	$71.30	5.297%	$75.0768	$75.08	$75.10	$75.10
Purchase #7	$16.49	5.872%	$17.4583	$17.46	$17.45	$17.50
7 purchase totals =	$902.89		$978.4692	$978.48	$978.50	$978.60