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	$108.84	10.168%	$119.9069	$119.91	$119.90	$119.90
Purchase #2	$47.73	11.190%	$53.071	$53.07	$53.05	$53.10
Purchase #3	$35.68	13.470%	$40.4861	$40.49	$40.50	$40.50
Purchase #4	$154.42	9.815%	$169.5763	$169.58	$169.60	$169.60
Purchase #5	$246.49	7.547%	$265.0926	$265.09	$265.10	$265.10
Purchase #6	$168.26	10.608%	$186.109	$186.11	$186.10	$186.10
Purchase #7	$103.32	7.491%	$111.0597	$111.06	$111.05	$111.10
7 purchase totals =	$864.74		$945.3016	$945.31	$945.30	$945.40