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	$35.87	13.608%	$40.7512	$40.75	$40.75	$40.80
Purchase #2	$102.93	8.698%	$111.8829	$111.88	$111.90	$111.90
Purchase #3	$19.56	10.463%	$21.6066	$21.61	$21.60	$21.60
Purchase #4	$227.33	7.142%	$243.5659	$243.57	$243.55	$243.60
Purchase #5	$88.80	13.529%	$100.8138	$100.81	$100.80	$100.80
Purchase #6	$32.55	9.667%	$35.6966	$35.70	$35.70	$35.70
Purchase #7	$153.28	7.580%	$164.8986	$164.90	$164.90	$164.90
7 purchase totals =	$660.32		$719.2156	$719.22	$719.20	$719.30