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	$187.85	10.869%	$208.2674	$208.27	$208.25	$208.30
Purchase #2	$22.59	13.612%	$25.665	$25.67	$25.65	$25.70
Purchase #3	$31.42	13.306%	$35.6007	$35.60	$35.60	$35.60
Purchase #4	$40.70	4.122%	$42.3777	$42.38	$42.40	$42.40
Purchase #5	$96.92	6.483%	$103.2033	$103.20	$103.20	$103.20
Purchase #6	$44.98	11.842%	$50.3065	$50.31	$50.30	$50.30
Purchase #7	$220.38	10.787%	$244.1524	$244.15	$244.15	$244.20
7 purchase totals =	$644.84		$709.5730	$709.58	$709.55	$709.70