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	$76.40	9.350%	$83.5434	$83.54	$83.55	$83.50
Purchase #2	$86.72	6.104%	$92.0134	$92.01	$92.00	$92.00
Purchase #3	$113.82	3.872%	$118.2271	$118.23	$118.25	$118.20
Purchase #4	$172.71	13.771%	$196.4939	$196.49	$196.50	$196.50
Purchase #5	$237.70	13.449%	$269.6683	$269.67	$269.65	$269.70
Purchase #6	$214.83	8.224%	$232.4976	$232.50	$232.50	$232.50
Purchase #7	$99.69	11.821%	$111.4744	$111.47	$111.45	$111.50
7 purchase totals =	$1,001.87		$1,103.9181	$1,103.91	$1,103.90	$1,103.90