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	$127.48	3.150%	$131.4956	$131.50	$131.50	$131.50
Purchase #2	$178.98	13.689%	$203.4806	$203.48	$203.50	$203.50
Purchase #3	$178.64	6.492%	$190.2373	$190.24	$190.25	$190.20
Purchase #4	$157.90	13.848%	$179.766	$179.77	$179.75	$179.80
Purchase #5	$56.51	5.214%	$59.4564	$59.46	$59.45	$59.50
Purchase #6	$137.52	6.497%	$146.4547	$146.45	$146.45	$146.50
Purchase #7	$97.74	7.622%	$105.1897	$105.19	$105.20	$105.20
7 purchase totals =	$934.77		$1,016.0803	$1,016.09	$1,016.10	$1,016.20