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	$79.45	9.332%	$86.8643	$86.86	$86.85	$86.90
Purchase #2	$94.46	4.466%	$98.6786	$98.68	$98.70	$98.70
Purchase #3	$105.60	7.214%	$113.218	$113.22	$113.20	$113.20
Purchase #4	$39.78	9.615%	$43.6048	$43.60	$43.60	$43.60
Purchase #5	$6.61	12.622%	$7.4443	$7.44	$7.45	$7.40
Purchase #6	$20.72	3.411%	$21.4268	$21.43	$21.45	$21.40
Purchase #7	$97.89	8.730%	$106.4358	$106.44	$106.45	$106.40
7 purchase totals =	$444.51		$477.6726	$477.67	$477.70	$477.60