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	$181.93	3.240%	$187.8245	$187.82	$187.80	$187.80
Purchase #2	$65.42	11.271%	$72.7935	$72.79	$72.80	$72.80
Purchase #3	$91.92	9.622%	$100.7645	$100.76	$100.75	$100.80
Purchase #4	$118.64	4.603%	$124.101	$124.10	$124.10	$124.10
Purchase #5	$50.45	10.136%	$55.5636	$55.56	$55.55	$55.60
Purchase #6	$94.99	9.605%	$104.1138	$104.11	$104.10	$104.10
Purchase #7	$249.88	3.757%	$259.268	$259.27	$259.25	$259.30
7 purchase totals =	$853.23		$904.4289	$904.41	$904.35	$904.50