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	$98.69	10.548%	$109.0998	$109.10	$109.10	$109.10
Purchase #2	$79.94	12.768%	$90.1467	$90.15	$90.15	$90.10
Purchase #3	$182.46	3.238%	$188.3681	$188.37	$188.35	$188.40
Purchase #4	$218.89	12.701%	$246.6912	$246.69	$246.70	$246.70
Purchase #5	$235.70	11.535%	$262.888	$262.89	$262.90	$262.90
Purchase #6	$117.98	5.622%	$124.6128	$124.61	$124.60	$124.60
Purchase #7	$42.89	3.651%	$44.4559	$44.46	$44.45	$44.50
7 purchase totals =	$976.55		$1,066.2625	$1,066.27	$1,066.25	$1,066.30