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	$137.70	10.413%	$152.0387	$152.04	$152.05	$152.00
Purchase #2	$142.76	9.549%	$156.3922	$156.39	$156.40	$156.40
Purchase #3	$217.26	5.196%	$228.5488	$228.55	$228.55	$228.50
Purchase #4	$105.53	11.566%	$117.7356	$117.74	$117.75	$117.70
Purchase #5	$86.38	4.516%	$90.2809	$90.28	$90.30	$90.30
Purchase #6	$161.94	6.520%	$172.4985	$172.50	$172.50	$172.50
Purchase #7	$157.61	4.351%	$164.4676	$164.47	$164.45	$164.50
7 purchase totals =	$1,009.18		$1,081.9623	$1,081.97	$1,082.00	$1,081.90