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	$227.59	9.663%	$249.582	$249.58	$249.60	$249.60
Purchase #2	$181.83	8.275%	$196.8764	$196.88	$196.90	$196.90
Purchase #3	$11.41	11.822%	$12.7589	$12.76	$12.75	$12.80
Purchase #4	$250.28	3.525%	$259.1024	$259.10	$259.10	$259.10
Purchase #5	$5.30	11.591%	$5.9143	$5.91	$5.90	$5.90
Purchase #6	$186.39	11.692%	$208.1827	$208.18	$208.20	$208.20
Purchase #7	$222.78	5.299%	$234.5851	$234.59	$234.60	$234.60
7 purchase totals =	$1,085.58		$1,167.0018	$1,167.00	$1,167.05	$1,167.10