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	$104.39	13.476%	$118.4576	$118.46	$118.45	$118.50
Purchase #2	$168.45	12.241%	$189.07	$189.07	$189.05	$189.10
Purchase #3	$11.58	7.213%	$12.4153	$12.42	$12.40	$12.40
Purchase #4	$100.77	8.611%	$109.4473	$109.45	$109.45	$109.40
Purchase #5	$106.50	13.448%	$120.8221	$120.82	$120.80	$120.80
Purchase #6	$28.51	13.156%	$32.2608	$32.26	$32.25	$32.30
Purchase #7	$236.61	13.602%	$268.7937	$268.79	$268.80	$268.80
7 purchase totals =	$756.81		$851.2668	$851.27	$851.20	$851.30