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	$141.89	9.148%	$154.8701	$154.87	$154.85	$154.90
Purchase #2	$201.95	3.637%	$209.2949	$209.29	$209.30	$209.30
Purchase #3	$169.99	11.527%	$189.5847	$189.58	$189.60	$189.60
Purchase #4	$232.61	11.725%	$259.8835	$259.88	$259.90	$259.90
Purchase #5	$118.98	4.347%	$124.1521	$124.15	$124.15	$124.20
Purchase #6	$62.94	13.469%	$71.4174	$71.42	$71.40	$71.40
Purchase #7	$80.57	13.863%	$91.7394	$91.74	$91.75	$91.70
7 purchase totals =	$1,008.93		$1,100.9421	$1,100.93	$1,100.95	$1,101.00