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	$241.32	5.503%	$254.5998	$254.60	$254.60	$254.60
Purchase #2	$75.89	12.472%	$85.355	$85.36	$85.35	$85.40
Purchase #3	$68.31	3.262%	$70.5383	$70.54	$70.55	$70.50
Purchase #4	$248.47	8.719%	$270.1341	$270.13	$270.15	$270.10
Purchase #5	$88.48	7.720%	$95.3107	$95.31	$95.30	$95.30
Purchase #6	$206.37	11.579%	$230.2656	$230.27	$230.25	$230.30
Purchase #7	$56.98	4.359%	$59.4638	$59.46	$59.45	$59.50
7 purchase totals =	$985.82		$1,065.6673	$1,065.67	$1,065.65	$1,065.70