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	$90.27	7.758%	$97.2731	$97.27	$97.25	$97.30
Purchase #2	$104.61	10.444%	$115.5355	$115.54	$115.55	$115.50
Purchase #3	$64.38	12.451%	$72.396	$72.40	$72.40	$72.40
Purchase #4	$192.43	11.256%	$214.0899	$214.09	$214.10	$214.10
Purchase #5	$250.88	13.299%	$284.2445	$284.24	$284.25	$284.20
Purchase #6	$167.95	8.858%	$182.827	$182.83	$182.85	$182.80
Purchase #7	$188.28	6.307%	$200.1548	$200.15	$200.15	$200.20
7 purchase totals =	$1,058.80		$1,166.5208	$1,166.52	$1,166.55	$1,166.50