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	$193.50	5.510%	$204.1619	$204.16	$204.15	$204.20
Purchase #2	$64.93	11.802%	$72.593	$72.59	$72.60	$72.60
Purchase #3	$230.34	12.757%	$259.7245	$259.72	$259.70	$259.70
Purchase #4	$178.71	6.836%	$190.9266	$190.93	$190.95	$190.90
Purchase #5	$35.80	4.244%	$37.3194	$37.32	$37.30	$37.30
Purchase #6	$13.55	11.710%	$15.1367	$15.14	$15.15	$15.10
Purchase #7	$177.73	12.490%	$199.9285	$199.93	$199.95	$199.90
7 purchase totals =	$894.56		$979.7906	$979.79	$979.80	$979.70