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	$149.86	11.683%	$167.3681	$167.37	$167.35	$167.40
Purchase #2	$89.54	5.588%	$94.5435	$94.54	$94.55	$94.50
Purchase #3	$143.88	8.745%	$156.4623	$156.46	$156.45	$156.50
Purchase #4	$169.40	13.664%	$192.5468	$192.55	$192.55	$192.50
Purchase #5	$111.80	4.210%	$116.5068	$116.51	$116.50	$116.50
Purchase #6	$226.34	12.430%	$254.4741	$254.47	$254.45	$254.50
Purchase #7	$125.78	4.322%	$131.2162	$131.22	$131.20	$131.20
7 purchase totals =	$1,016.60		$1,113.1178	$1,113.12	$1,113.05	$1,113.10