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	$150.74	7.833%	$162.5475	$162.55	$162.55	$162.50
Purchase #2	$143.80	7.625%	$154.7648	$154.76	$154.75	$154.80
Purchase #3	$235.60	13.162%	$266.6097	$266.61	$266.60	$266.60
Purchase #4	$47.74	13.645%	$54.2541	$54.25	$54.25	$54.30
Purchase #5	$55.72	7.400%	$59.8433	$59.84	$59.85	$59.80
Purchase #6	$134.96	12.221%	$151.4535	$151.45	$151.45	$151.50
Purchase #7	$53.93	10.430%	$59.5549	$59.55	$59.55	$59.60
7 purchase totals =	$822.49		$909.0278	$909.01	$909.00	$909.10