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	$170.45	10.607%	$188.5296	$188.53	$188.55	$188.50
Purchase #2	$11.37	4.370%	$11.8669	$11.87	$11.85	$11.90
Purchase #3	$67.30	5.820%	$71.2169	$71.22	$71.20	$71.20
Purchase #4	$84.41	7.371%	$90.6319	$90.63	$90.65	$90.60
Purchase #5	$13.51	3.296%	$13.9553	$13.96	$13.95	$14.00
Purchase #6	$63.63	4.277%	$66.3515	$66.35	$66.35	$66.40
Purchase #7	$155.27	13.718%	$176.5699	$176.57	$176.55	$176.60
7 purchase totals =	$565.94		$619.1220	$619.13	$619.10	$619.20