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	$147.98	5.602%	$156.2698	$156.27	$156.25	$156.30
Purchase #2	$173.73	8.279%	$188.1131	$188.11	$188.10	$188.10
Purchase #3	$40.29	7.445%	$43.2896	$43.29	$43.30	$43.30
Purchase #4	$78.35	10.421%	$86.5149	$86.51	$86.50	$86.50
Purchase #5	$241.70	9.843%	$265.4905	$265.49	$265.50	$265.50
Purchase #6	$121.70	5.396%	$128.2669	$128.27	$128.25	$128.30
Purchase #7	$18.64	4.437%	$19.4671	$19.47	$19.45	$19.50
7 purchase totals =	$822.39		$887.4119	$887.41	$887.35	$887.50