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	$213.93	10.274%	$235.9092	$235.91	$235.90	$235.90
Purchase #2	$160.80	4.182%	$167.5247	$167.52	$167.50	$167.50
Purchase #3	$42.70	5.115%	$44.8841	$44.88	$44.90	$44.90
Purchase #4	$131.82	7.605%	$141.8449	$141.84	$141.85	$141.80
Purchase #5	$7.34	3.676%	$7.6098	$7.61	$7.60	$7.60
Purchase #6	$205.61	13.402%	$233.1659	$233.17	$233.15	$233.20
Purchase #7	$167.73	10.547%	$185.4205	$185.42	$185.40	$185.40
7 purchase totals =	$929.93		$1,016.3591	$1,016.35	$1,016.30	$1,016.30