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	$73.77	3.555%	$76.3925	$76.39	$76.40	$76.40
Purchase #2	$224.27	6.829%	$239.5854	$239.59	$239.60	$239.60
Purchase #3	$82.87	8.525%	$89.9347	$89.93	$89.95	$89.90
Purchase #4	$10.50	4.254%	$10.9467	$10.95	$10.95	$10.90
Purchase #5	$219.79	6.375%	$233.8016	$233.80	$233.80	$233.80
Purchase #6	$18.99	11.485%	$21.171	$21.17	$21.15	$21.20
Purchase #7	$31.83	3.845%	$33.0539	$33.05	$33.05	$33.10
7 purchase totals =	$662.02		$704.8858	$704.88	$704.90	$704.90