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	$215.34	8.541%	$233.7322	$233.73	$233.75	$233.70
Purchase #2	$158.77	5.746%	$167.8929	$167.89	$167.90	$167.90
Purchase #3	$200.59	8.724%	$218.0895	$218.09	$218.10	$218.10
Purchase #4	$66.50	9.139%	$72.5774	$72.58	$72.60	$72.60
Purchase #5	$39.96	7.786%	$43.0713	$43.07	$43.05	$43.10
Purchase #6	$220.41	10.808%	$244.2319	$244.23	$244.25	$244.20
Purchase #7	$117.37	9.131%	$128.0871	$128.09	$128.10	$128.10
7 purchase totals =	$1,018.94		$1,107.6823	$1,107.68	$1,107.75	$1,107.70