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	$167.54	8.789%	$182.2651	$182.27	$182.25	$182.30
Purchase #2	$85.85	6.777%	$91.6681	$91.67	$91.65	$91.70
Purchase #3	$205.90	9.466%	$225.3905	$225.39	$225.40	$225.40
Purchase #4	$132.54	5.850%	$140.2936	$140.29	$140.30	$140.30
Purchase #5	$129.89	8.445%	$140.8592	$140.86	$140.85	$140.90
Purchase #6	$132.42	8.112%	$143.1619	$143.16	$143.15	$143.20
Purchase #7	$24.87	10.491%	$27.4791	$27.48	$27.50	$27.50
7 purchase totals =	$879.01		$951.1175	$951.12	$951.10	$951.30