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	$152.41	4.190%	$158.796	$158.80	$158.80	$158.80
Purchase #2	$144.79	3.839%	$150.3485	$150.35	$150.35	$150.30
Purchase #3	$25.38	4.327%	$26.4782	$26.48	$26.50	$26.50
Purchase #4	$152.83	3.700%	$158.4847	$158.48	$158.50	$158.50
Purchase #5	$63.87	12.358%	$71.7631	$71.76	$71.75	$71.80
Purchase #6	$203.93	5.720%	$215.5948	$215.59	$215.60	$215.60
Purchase #7	$95.87	5.843%	$101.4717	$101.47	$101.45	$101.50
7 purchase totals =	$839.08		$882.9370	$882.93	$882.95	$883.00