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	$70.64	7.784%	$76.1386	$76.14	$76.15	$76.10
Purchase #2	$95.41	5.745%	$100.8913	$100.89	$100.90	$100.90
Purchase #3	$157.84	11.737%	$176.3657	$176.37	$176.35	$176.40
Purchase #4	$213.39	11.730%	$238.4206	$238.42	$238.40	$238.40
Purchase #5	$174.99	6.639%	$186.6076	$186.61	$186.60	$186.60
Purchase #6	$85.47	12.853%	$96.4555	$96.46	$96.45	$96.50
Purchase #7	$35.42	13.256%	$40.1153	$40.12	$40.10	$40.10
7 purchase totals =	$833.16		$914.9946	$915.01	$914.95	$915.00