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	$101.33	13.303%	$114.8099	$114.81	$114.80	$114.80
Purchase #2	$242.76	7.229%	$260.3091	$260.31	$260.30	$260.30
Purchase #3	$231.95	3.727%	$240.5948	$240.59	$240.60	$240.60
Purchase #4	$250.97	7.770%	$270.4704	$270.47	$270.45	$270.50
Purchase #5	$242.90	5.341%	$255.8733	$255.87	$255.85	$255.90
Purchase #6	$124.77	13.145%	$141.171	$141.17	$141.15	$141.20
Purchase #7	$196.63	10.798%	$217.8621	$217.86	$217.85	$217.90
7 purchase totals =	$1,391.31		$1,501.0906	$1,501.08	$1,501.00	$1,501.20