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	$107.86	9.124%	$117.7011	$117.70	$117.70	$117.70
Purchase #2	$100.69	10.742%	$111.5061	$111.51	$111.50	$111.50
Purchase #3	$7.67	11.832%	$8.5775	$8.58	$8.60	$8.60
Purchase #4	$94.45	4.866%	$99.0459	$99.05	$99.05	$99.00
Purchase #5	$165.39	12.121%	$185.4369	$185.44	$185.45	$185.40
Purchase #6	$155.80	12.134%	$174.7048	$174.70	$174.70	$174.70
Purchase #7	$25.39	7.670%	$27.3374	$27.34	$27.35	$27.30
7 purchase totals =	$657.25		$724.3097	$724.32	$724.35	$724.20