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	$164.49	12.236%	$184.617	$184.62	$184.60	$184.60
Purchase #2	$46.90	8.812%	$51.0328	$51.03	$51.05	$51.00
Purchase #3	$236.31	8.372%	$256.0939	$256.09	$256.10	$256.10
Purchase #4	$154.65	6.749%	$165.0873	$165.09	$165.10	$165.10
Purchase #5	$132.76	6.553%	$141.4598	$141.46	$141.45	$141.50
Purchase #6	$198.67	13.157%	$224.809	$224.81	$224.80	$224.80
Purchase #7	$69.69	11.372%	$77.6151	$77.62	$77.60	$77.60
7 purchase totals =	$1,003.47		$1,100.7149	$1,100.72	$1,100.70	$1,100.70