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	$55.74	12.139%	$62.5063	$62.51	$62.50	$62.50
Purchase #2	$71.60	4.429%	$74.7712	$74.77	$74.75	$74.80
Purchase #3	$187.80	4.674%	$196.5778	$196.58	$196.60	$196.60
Purchase #4	$112.73	6.207%	$119.7272	$119.73	$119.75	$119.70
Purchase #5	$244.41	7.482%	$262.6968	$262.70	$262.70	$262.70
Purchase #6	$215.82	3.302%	$222.9464	$222.95	$222.95	$222.90
Purchase #7	$97.36	3.402%	$100.6722	$100.67	$100.65	$100.70
7 purchase totals =	$985.46		$1,039.8979	$1,039.91	$1,039.90	$1,039.90