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	$100.59	9.219%	$109.8634	$109.86	$109.85	$109.90
Purchase #2	$18.87	7.481%	$20.2817	$20.28	$20.30	$20.30
Purchase #3	$246.26	4.167%	$256.5217	$256.52	$256.50	$256.50
Purchase #4	$161.39	3.705%	$167.3695	$167.37	$167.35	$167.40
Purchase #5	$43.29	7.581%	$46.5718	$46.57	$46.55	$46.60
Purchase #6	$112.51	13.125%	$127.2769	$127.28	$127.30	$127.30
Purchase #7	$68.96	9.385%	$75.4319	$75.43	$75.45	$75.40
7 purchase totals =	$751.87		$803.3169	$803.31	$803.30	$803.40