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	$70.26	3.274%	$72.5603	$72.56	$72.55	$72.60
Purchase #2	$94.45	7.185%	$101.2362	$101.24	$101.25	$101.20
Purchase #3	$166.27	5.713%	$175.769	$175.77	$175.75	$175.80
Purchase #4	$136.48	6.715%	$145.6446	$145.64	$145.65	$145.60
Purchase #5	$238.25	12.684%	$268.4696	$268.47	$268.45	$268.50
Purchase #6	$132.34	12.264%	$148.5702	$148.57	$148.55	$148.60
Purchase #7	$27.55	8.154%	$29.7964	$29.80	$29.80	$29.80
7 purchase totals =	$865.60		$942.0463	$942.05	$942.00	$942.10