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	$152.68	12.861%	$172.3162	$172.32	$172.30	$172.30
Purchase #2	$150.31	5.457%	$158.5124	$158.51	$158.50	$158.50
Purchase #3	$92.78	3.483%	$96.0115	$96.01	$96.00	$96.00
Purchase #4	$92.47	7.432%	$99.3424	$99.34	$99.35	$99.30
Purchase #5	$191.84	4.570%	$200.6071	$200.61	$200.60	$200.60
Purchase #6	$21.92	3.806%	$22.7543	$22.75	$22.75	$22.80
Purchase #7	$166.67	10.687%	$184.482	$184.48	$184.50	$184.50
7 purchase totals =	$868.67		$934.0259	$934.02	$934.00	$934.00