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	$244.76	5.695%	$258.6991	$258.70	$258.70	$258.70
Purchase #2	$185.50	13.531%	$210.6	$210.60	$210.60	$210.60
Purchase #3	$113.72	4.526%	$118.867	$118.87	$118.85	$118.90
Purchase #4	$142.74	8.168%	$154.399	$154.40	$154.40	$154.40
Purchase #5	$43.70	12.720%	$49.2586	$49.26	$49.25	$49.30
Purchase #6	$238.45	6.644%	$254.2926	$254.29	$254.30	$254.30
Purchase #7	$73.74	4.265%	$76.885	$76.89	$76.90	$76.90
7 purchase totals =	$1,042.61		$1,123.0013	$1,123.01	$1,123.00	$1,123.10