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	$141.54	6.193%	$150.3056	$150.31	$150.30	$150.30
Purchase #2	$70.84	7.302%	$76.0127	$76.01	$76.00	$76.00
Purchase #3	$109.37	12.669%	$123.2261	$123.23	$123.25	$123.20
Purchase #4	$215.97	8.312%	$233.9214	$233.92	$233.90	$233.90
Purchase #5	$79.35	5.663%	$83.8436	$83.84	$83.85	$83.80
Purchase #6	$127.89	10.734%	$141.6177	$141.62	$141.60	$141.60
Purchase #7	$140.75	3.192%	$145.2427	$145.24	$145.25	$145.20
7 purchase totals =	$885.71		$954.1698	$954.17	$954.15	$954.00