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	$103.90	11.787%	$116.1467	$116.15	$116.15	$116.10
Purchase #2	$226.53	12.865%	$255.6731	$255.67	$255.65	$255.70
Purchase #3	$208.31	7.807%	$224.5728	$224.57	$224.55	$224.60
Purchase #4	$68.73	5.293%	$72.3679	$72.37	$72.35	$72.40
Purchase #5	$52.99	11.462%	$59.0637	$59.06	$59.05	$59.10
Purchase #6	$65.67	12.791%	$74.0698	$74.07	$74.05	$74.10
Purchase #7	$249.29	3.783%	$258.7206	$258.72	$258.70	$258.70
7 purchase totals =	$975.42		$1,060.6146	$1,060.61	$1,060.50	$1,060.70