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	$37.87	9.295%	$41.39	$41.39	$41.40	$41.40
Purchase #2	$75.30	4.758%	$78.8828	$78.88	$78.90	$78.90
Purchase #3	$114.30	3.811%	$118.656	$118.66	$118.65	$118.70
Purchase #4	$204.25	9.610%	$223.8784	$223.88	$223.90	$223.90
Purchase #5	$15.95	12.263%	$17.9059	$17.91	$17.90	$17.90
Purchase #6	$186.77	5.189%	$196.4615	$196.46	$196.45	$196.50
Purchase #7	$79.94	11.165%	$88.8653	$88.87	$88.85	$88.90
7 purchase totals =	$714.38		$766.0399	$766.05	$766.05	$766.20