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	$52.31	10.153%	$57.621	$57.62	$57.60	$57.60
Purchase #2	$145.61	6.207%	$154.648	$154.65	$154.65	$154.60
Purchase #3	$71.72	10.815%	$79.4765	$79.48	$79.50	$79.50
Purchase #4	$118.53	4.510%	$123.8757	$123.88	$123.90	$123.90
Purchase #5	$45.63	10.124%	$50.2496	$50.25	$50.25	$50.20
Purchase #6	$175.79	5.352%	$185.1983	$185.20	$185.20	$185.20
Purchase #7	$38.52	7.858%	$41.5469	$41.55	$41.55	$41.50
7 purchase totals =	$648.11		$692.6160	$692.63	$692.65	$692.50