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	$48.69	5.619%	$51.4259	$51.43	$51.45	$51.40
Purchase #2	$50.43	3.426%	$52.1577	$52.16	$52.15	$52.20
Purchase #3	$189.29	10.561%	$209.2809	$209.28	$209.30	$209.30
Purchase #4	$9.95	3.626%	$10.3108	$10.31	$10.30	$10.30
Purchase #5	$216.41	11.164%	$240.57	$240.57	$240.55	$240.60
Purchase #6	$215.29	3.391%	$222.5905	$222.59	$222.60	$222.60
Purchase #7	$113.26	5.845%	$119.88	$119.88	$119.90	$119.90
7 purchase totals =	$843.32		$906.2158	$906.22	$906.25	$906.30