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	$53.36	10.151%	$58.7766	$58.78	$58.80	$58.80
Purchase #2	$123.80	5.240%	$130.2871	$130.29	$130.30	$130.30
Purchase #3	$30.42	9.542%	$33.3227	$33.32	$33.30	$33.30
Purchase #4	$101.58	7.836%	$109.5398	$109.54	$109.55	$109.50
Purchase #5	$246.89	5.724%	$261.022	$261.02	$261.00	$261.00
Purchase #6	$159.69	5.816%	$168.9776	$168.98	$169.00	$169.00
Purchase #7	$241.87	3.186%	$249.576	$249.58	$249.60	$249.60
7 purchase totals =	$957.61		$1,011.5018	$1,011.51	$1,011.55	$1,011.50