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	$209.86	11.566%	$234.1324	$234.13	$234.15	$234.10
Purchase #2	$151.89	9.354%	$166.0978	$166.10	$166.10	$166.10
Purchase #3	$174.56	12.577%	$196.5144	$196.51	$196.50	$196.50
Purchase #4	$70.58	11.224%	$78.5019	$78.50	$78.50	$78.50
Purchase #5	$238.83	5.807%	$252.6989	$252.70	$252.70	$252.70
Purchase #6	$119.94	12.336%	$134.7358	$134.74	$134.75	$134.70
Purchase #7	$216.41	13.618%	$245.8807	$245.88	$245.90	$245.90
7 purchase totals =	$1,182.07		$1,308.5619	$1,308.56	$1,308.60	$1,308.50