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	$126.59	13.368%	$143.5126	$143.51	$143.50	$143.50
Purchase #2	$18.47	7.609%	$19.8754	$19.88	$19.90	$19.90
Purchase #3	$236.98	11.602%	$264.4744	$264.47	$264.45	$264.50
Purchase #4	$229.64	12.143%	$257.5252	$257.53	$257.55	$257.50
Purchase #5	$104.38	13.693%	$118.6728	$118.67	$118.65	$118.70
Purchase #6	$155.82	10.335%	$171.924	$171.92	$171.90	$171.90
Purchase #7	$162.78	13.423%	$184.63	$184.63	$184.65	$184.60
7 purchase totals =	$1,034.66		$1,160.6144	$1,160.61	$1,160.60	$1,160.60