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	$182.69	12.468%	$205.4678	$205.47	$205.45	$205.50
Purchase #2	$193.86	13.424%	$219.8838	$219.88	$219.90	$219.90
Purchase #3	$173.87	10.115%	$191.457	$191.46	$191.45	$191.50
Purchase #4	$132.87	11.446%	$148.0783	$148.08	$148.10	$148.10
Purchase #5	$97.86	6.366%	$104.0898	$104.09	$104.10	$104.10
Purchase #6	$98.86	5.221%	$104.0215	$104.02	$104.00	$104.00
Purchase #7	$147.91	10.128%	$162.8903	$162.89	$162.90	$162.90
7 purchase totals =	$1,027.92		$1,135.8885	$1,135.89	$1,135.90	$1,136.00