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	$53.96	9.870%	$59.2859	$59.29	$59.30	$59.30
Purchase #2	$222.27	13.140%	$251.4763	$251.48	$251.50	$251.50
Purchase #3	$27.94	5.637%	$29.515	$29.52	$29.50	$29.50
Purchase #4	$22.68	7.640%	$24.4128	$24.41	$24.40	$24.40
Purchase #5	$158.77	11.123%	$176.43	$176.43	$176.45	$176.40
Purchase #6	$220.82	8.833%	$240.325	$240.33	$240.35	$240.30
Purchase #7	$88.86	13.819%	$101.1396	$101.14	$101.15	$101.10
7 purchase totals =	$795.30		$882.5846	$882.60	$882.65	$882.50