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	$249.63	9.217%	$272.6384	$272.64	$272.65	$272.60
Purchase #2	$127.54	4.122%	$132.7972	$132.80	$132.80	$132.80
Purchase #3	$59.34	13.746%	$67.4969	$67.50	$67.50	$67.50
Purchase #4	$198.87	4.801%	$208.4177	$208.42	$208.40	$208.40
Purchase #5	$104.56	11.461%	$116.5436	$116.54	$116.55	$116.50
Purchase #6	$245.46	10.476%	$271.1744	$271.17	$271.15	$271.20
Purchase #7	$35.76	6.621%	$38.1277	$38.13	$38.15	$38.10
7 purchase totals =	$1,021.16		$1,107.1959	$1,107.20	$1,107.20	$1,107.10