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	$94.89	13.137%	$107.3557	$107.36	$107.35	$107.40
Purchase #2	$46.87	10.258%	$51.6779	$51.68	$51.70	$51.70
Purchase #3	$147.54	10.359%	$162.8237	$162.82	$162.80	$162.80
Purchase #4	$27.68	4.414%	$28.9018	$28.90	$28.90	$28.90
Purchase #5	$11.79	13.357%	$13.3648	$13.36	$13.35	$13.40
Purchase #6	$46.87	11.591%	$52.3027	$52.30	$52.30	$52.30
Purchase #7	$24.78	10.816%	$27.4602	$27.46	$27.45	$27.50
7 purchase totals =	$400.42		$443.8868	$443.88	$443.85	$444.00