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	$123.88	3.278%	$127.9408	$127.94	$127.95	$127.90
Purchase #2	$49.54	10.452%	$54.7179	$54.72	$54.70	$54.70
Purchase #3	$245.51	6.826%	$262.2685	$262.27	$262.25	$262.30
Purchase #4	$197.28	10.410%	$217.8168	$217.82	$217.80	$217.80
Purchase #5	$79.27	11.398%	$88.3052	$88.31	$88.30	$88.30
Purchase #6	$19.68	6.691%	$20.9968	$21.00	$21.00	$21.00
Purchase #7	$167.90	3.844%	$174.3541	$174.35	$174.35	$174.40
7 purchase totals =	$883.06		$946.4001	$946.41	$946.35	$946.40