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	$20.51	11.179%	$22.8028	$22.80	$22.80	$22.80
Purchase #2	$62.77	8.817%	$68.3044	$68.30	$68.30	$68.30
Purchase #3	$200.88	8.297%	$217.547	$217.55	$217.55	$217.50
Purchase #4	$65.25	11.102%	$72.4941	$72.49	$72.50	$72.50
Purchase #5	$203.86	9.653%	$223.5386	$223.54	$223.55	$223.50
Purchase #6	$160.54	8.102%	$173.547	$173.55	$173.55	$173.50
Purchase #7	$233.92	8.276%	$253.2792	$253.28	$253.30	$253.30
7 purchase totals =	$947.73		$1,031.5131	$1,031.51	$1,031.55	$1,031.40