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	$132.43	13.588%	$150.4246	$150.42	$150.40	$150.40
Purchase #2	$237.75	10.607%	$262.9681	$262.97	$262.95	$263.00
Purchase #3	$149.44	4.738%	$156.5205	$156.52	$156.50	$156.50
Purchase #4	$53.26	13.300%	$60.3436	$60.34	$60.35	$60.30
Purchase #5	$114.40	11.383%	$127.4222	$127.42	$127.40	$127.40
Purchase #6	$58.85	4.650%	$61.5865	$61.59	$61.60	$61.60
Purchase #7	$179.89	9.263%	$196.5532	$196.55	$196.55	$196.60
7 purchase totals =	$926.02		$1,015.8187	$1,015.81	$1,015.75	$1,015.80