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	$41.72	4.262%	$43.4981	$43.50	$43.50	$43.50
Purchase #2	$82.95	11.382%	$92.3914	$92.39	$92.40	$92.40
Purchase #3	$178.42	9.523%	$195.4109	$195.41	$195.40	$195.40
Purchase #4	$120.43	8.835%	$131.07	$131.07	$131.05	$131.10
Purchase #5	$195.38	11.695%	$218.2297	$218.23	$218.25	$218.20
Purchase #6	$195.56	11.778%	$218.5931	$218.59	$218.60	$218.60
Purchase #7	$55.27	9.537%	$60.5411	$60.54	$60.55	$60.50
7 purchase totals =	$869.73		$959.7343	$959.73	$959.75	$959.70