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	$225.38	4.470%	$235.4545	$235.45	$235.45	$235.50
Purchase #2	$54.60	12.339%	$61.3371	$61.34	$61.35	$61.30
Purchase #3	$239.42	8.860%	$260.6326	$260.63	$260.65	$260.60
Purchase #4	$146.58	12.484%	$164.879	$164.88	$164.90	$164.90
Purchase #5	$46.77	11.271%	$52.0414	$52.04	$52.05	$52.00
Purchase #6	$143.97	11.712%	$160.8318	$160.83	$160.85	$160.80
Purchase #7	$72.91	12.449%	$81.9866	$81.99	$82.00	$82.00
7 purchase totals =	$929.63		$1,017.1630	$1,017.16	$1,017.25	$1,017.10