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	$219.42	12.307%	$246.424	$246.42	$246.40	$246.40
Purchase #2	$31.47	3.218%	$32.4827	$32.48	$32.50	$32.50
Purchase #3	$167.27	5.554%	$176.5602	$176.56	$176.55	$176.60
Purchase #4	$14.37	7.789%	$15.4893	$15.49	$15.50	$15.50
Purchase #5	$220.54	5.701%	$233.113	$233.11	$233.10	$233.10
Purchase #6	$96.38	7.112%	$103.2345	$103.23	$103.25	$103.20
Purchase #7	$226.43	3.714%	$234.8396	$234.84	$234.85	$234.80
7 purchase totals =	$975.88		$1,042.1433	$1,042.13	$1,042.15	$1,042.10