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	$23.66	3.304%	$24.4417	$24.44	$24.45	$24.40
Purchase #2	$33.26	6.472%	$35.4126	$35.41	$35.40	$35.40
Purchase #3	$218.40	3.292%	$225.5897	$225.59	$225.60	$225.60
Purchase #4	$143.73	8.836%	$156.43	$156.43	$156.45	$156.40
Purchase #5	$157.49	4.685%	$164.8684	$164.87	$164.85	$164.90
Purchase #6	$212.25	9.789%	$233.0272	$233.03	$233.05	$233.00
Purchase #7	$129.59	11.507%	$144.5019	$144.50	$144.50	$144.50
7 purchase totals =	$918.38		$984.2715	$984.27	$984.30	$984.20