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	$27.48	4.504%	$28.7177	$28.72	$28.70	$28.70
Purchase #2	$73.25	11.241%	$81.484	$81.48	$81.50	$81.50
Purchase #3	$205.83	3.336%	$212.6965	$212.70	$212.70	$212.70
Purchase #4	$221.27	8.611%	$240.3236	$240.32	$240.30	$240.30
Purchase #5	$185.88	11.106%	$206.5238	$206.52	$206.50	$206.50
Purchase #6	$226.46	10.657%	$250.5938	$250.59	$250.60	$250.60
Purchase #7	$142.58	6.863%	$152.3653	$152.37	$152.35	$152.40
7 purchase totals =	$1,082.75		$1,172.7047	$1,172.70	$1,172.65	$1,172.70