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	$127.41	10.589%	$140.9014	$140.90	$140.90	$140.90
Purchase #2	$192.84	7.844%	$207.9664	$207.97	$207.95	$208.00
Purchase #3	$64.59	12.807%	$72.862	$72.86	$72.85	$72.90
Purchase #4	$91.97	13.150%	$104.0641	$104.06	$104.05	$104.10
Purchase #5	$183.88	3.414%	$190.1577	$190.16	$190.15	$190.20
Purchase #6	$126.81	8.282%	$137.3124	$137.31	$137.30	$137.30
Purchase #7	$87.53	13.196%	$99.0805	$99.08	$99.10	$99.10
7 purchase totals =	$875.03		$952.3445	$952.34	$952.30	$952.50