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	$232.59	11.472%	$259.2727	$259.27	$259.25	$259.30
Purchase #2	$232.74	7.256%	$249.6276	$249.63	$249.65	$249.60
Purchase #3	$172.84	4.587%	$180.7682	$180.77	$180.75	$180.80
Purchase #4	$100.41	5.352%	$105.7839	$105.78	$105.80	$105.80
Purchase #5	$34.77	8.787%	$37.8252	$37.83	$37.85	$37.80
Purchase #6	$95.96	10.270%	$105.8151	$105.82	$105.80	$105.80
Purchase #7	$99.68	3.468%	$103.1369	$103.14	$103.15	$103.10
7 purchase totals =	$968.99		$1,042.2296	$1,042.24	$1,042.25	$1,042.20