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	$200.69	5.394%	$211.5152	$211.52	$211.50	$211.50
Purchase #2	$40.30	12.523%	$45.3468	$45.35	$45.35	$45.30
Purchase #3	$250.61	11.354%	$279.0643	$279.06	$279.05	$279.10
Purchase #4	$24.45	11.169%	$27.1808	$27.18	$27.20	$27.20
Purchase #5	$116.32	7.333%	$124.8497	$124.85	$124.85	$124.80
Purchase #6	$203.47	11.481%	$226.8304	$226.83	$226.85	$226.80
Purchase #7	$172.77	11.276%	$192.2515	$192.25	$192.25	$192.30
7 purchase totals =	$1,008.61		$1,107.0387	$1,107.04	$1,107.05	$1,107.00