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	$137.50	9.763%	$150.9241	$150.92	$150.90	$150.90
Purchase #2	$70.59	9.820%	$77.5219	$77.52	$77.50	$77.50
Purchase #3	$157.32	13.505%	$178.5661	$178.57	$178.55	$178.60
Purchase #4	$95.31	9.188%	$104.0671	$104.07	$104.05	$104.10
Purchase #5	$36.36	8.536%	$39.4637	$39.46	$39.45	$39.50
Purchase #6	$144.96	11.817%	$162.0899	$162.09	$162.10	$162.10
Purchase #7	$67.54	12.269%	$75.8265	$75.83	$75.85	$75.80
7 purchase totals =	$709.58		$788.4593	$788.46	$788.40	$788.50