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	$79.61	3.706%	$82.5603	$82.56	$82.55	$82.60
Purchase #2	$158.45	10.723%	$175.4406	$175.44	$175.45	$175.40
Purchase #3	$163.66	3.632%	$169.6041	$169.60	$169.60	$169.60
Purchase #4	$78.89	4.809%	$82.6838	$82.68	$82.70	$82.70
Purchase #5	$183.76	5.788%	$194.396	$194.40	$194.40	$194.40
Purchase #6	$151.73	7.351%	$162.8837	$162.88	$162.90	$162.90
Purchase #7	$223.62	8.214%	$241.9881	$241.99	$242.00	$242.00
7 purchase totals =	$1,039.72		$1,109.5566	$1,109.55	$1,109.60	$1,109.60