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	$131.59	10.111%	$144.8951	$144.90	$144.90	$144.90
Purchase #2	$165.77	7.661%	$178.4696	$178.47	$178.45	$178.50
Purchase #3	$141.79	6.588%	$151.1311	$151.13	$151.15	$151.10
Purchase #4	$32.61	8.118%	$35.2573	$35.26	$35.25	$35.30
Purchase #5	$69.45	3.163%	$71.6467	$71.65	$71.65	$71.60
Purchase #6	$154.40	11.435%	$172.0556	$172.06	$172.05	$172.10
Purchase #7	$98.38	9.345%	$107.5736	$107.57	$107.55	$107.60
7 purchase totals =	$793.99		$861.0290	$861.04	$861.00	$861.10