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	$238.98	3.158%	$246.527	$246.53	$246.55	$246.50
Purchase #2	$205.71	7.267%	$220.6589	$220.66	$220.65	$220.70
Purchase #3	$78.95	4.805%	$82.7435	$82.74	$82.75	$82.70
Purchase #4	$19.95	4.727%	$20.893	$20.89	$20.90	$20.90
Purchase #5	$54.86	3.770%	$56.9282	$56.93	$56.95	$56.90
Purchase #6	$229.66	13.426%	$260.4942	$260.49	$260.50	$260.50
Purchase #7	$200.94	11.371%	$223.7889	$223.79	$223.80	$223.80
7 purchase totals =	$1,029.05		$1,112.0337	$1,112.03	$1,112.10	$1,112.00