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	$186.26	5.372%	$196.2659	$196.27	$196.25	$196.30
Purchase #2	$145.34	9.370%	$158.9584	$158.96	$158.95	$159.00
Purchase #3	$204.65	12.104%	$229.4208	$229.42	$229.40	$229.40
Purchase #4	$247.79	5.767%	$262.08	$262.08	$262.10	$262.10
Purchase #5	$38.82	11.665%	$43.3484	$43.35	$43.35	$43.30
Purchase #6	$180.97	8.602%	$196.537	$196.54	$196.55	$196.50
Purchase #7	$220.72	13.482%	$250.4775	$250.48	$250.50	$250.50
7 purchase totals =	$1,224.55		$1,337.0880	$1,337.10	$1,337.10	$1,337.10